General-Purpose, -55C to +125C, Wide Bandwidth, DC-Coupled VGA AD8336 Low noise Voltage noise: 3 nV/Hz Current noise: 3 pA/Hz Small-signal BW: 115 MHz Large-signal BW: 2 V p-p = 80 MHz Slew rate: 550 V/s, 2 V p-p Gain ranges (specified) -14 dB to +46 dB 0 dB to 60 dB Gain scaling: 50 dB/V DC-coupled Single-ended input and output Supplies: 3 V to 12 V Temperature range: -55C to +125C Power 150 mW @ 3 V, -55C < T < +125C 84 mW @ 3 V, PWRA = 3 V FUNCTIONAL BLOCK DIAGRAM AD8336 INPP 4 + INPN 5 - PRAO VGAI 8 9 ATTENUATOR -60dB TO 0dB PrA PWRA 2 34dB 1 VOUT GAIN CONTROL INTERFACE BIAS 10 13 3 11 12 VNEG VPOS VCOM GPOS GNEG 06228-001 FEATURES Figure 1. APPLICATIONS Industrial process controls High performance AGC systems I/Q signal processing Video Industrial and medical ultrasound Radar receivers GENERAL DESCRIPTION The AD8336 is a low noise, single-ended, linear-in-dB, generalpurpose variable gain amplifier, usable over a large range of supply voltages. It features an uncommitted preamplifier (preamp) with a usable gain range of 6 dB to 26 dB established by external resistors in the classical manner. The VGA gain range is 0 dB to 60 dB, and its absolute gain limits are -26 dB to +34 dB. When the preamplifier gain is adjusted for 12 dB, the combined 3 dB bandwidth of the preamp and VGA is 100 MHz, and the amplifier is fully usable to 80 MHz. With 5 V supplies, the maximum output swing is 7 V p-p. Thanks to its X-Amp(R) architecture, excellent bandwidth uniformity is maintained across the entire gain range of the VGA. Intended for a broad spectrum of applications, the differential gain control interface provides precise linear-in-dB gain scaling of 50 dB/V over the temperature span of -55C to +125C. The differential gain control is easy to interface with a variety of external circuits within the common-mode voltage limits of the AD8336. The large supply voltage range makes the AD8336 particularly suited for industrial medical applications and for video circuits. Dual-supply operation enables bipolar input signals, such as those generated by photodiodes or photomultiplier tubes. The fully independent voltage feedback preamp allows both inverting and noninverting gain topologies, making it a fully bipolar VGA. The AD8336 can be used within the specified gain range of -14 dB to +60 dB by selecting a preamp gain between 6 dB and 26 dB and choosing appropriate feedback resistors. For the nominal preamp gain of 4x, the overall gain range is -14 dB to +46 dB. In critical applications, the quiescent power can be reduced by about half by using the power adjust pin, PWRA. This is especially useful when operating with high supply voltages of up to 12 V, or at high temperatures. The operating temperature range is -55C to +125C. The AD8336 is available in a 16-lead LFCSP (4 mm x 4 mm). Rev. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2006-2011 Analog Devices, Inc. All rights reserved. AD8336 TABLE OF CONTENTS Features .............................................................................................. 1 VGA ............................................................................................. 20 Applications ....................................................................................... 1 Setting the Gain .......................................................................... 21 Functional Block Diagram .............................................................. 1 Noise ............................................................................................ 21 General Description ......................................................................... 1 Offset Voltage.............................................................................. 21 Revision History ............................................................................... 2 Applications Information .............................................................. 22 Specifications..................................................................................... 3 Amplifier Configuration ........................................................... 22 Absolute Maximum Ratings............................................................ 5 Preamplifier................................................................................. 22 ESD Caution .................................................................................. 5 Using the Power Adjust Feature ............................................... 23 Pin Configuration and Function Descriptions ............................. 6 Driving Capacitive Loads .......................................................... 23 Typical Performance Characteristics ............................................. 7 Evaluation Board ............................................................................ 24 Test Circuits ..................................................................................... 16 Optional Circuitry...................................................................... 24 Theory of Operation ...................................................................... 20 Board Layout Considerations ................................................... 24 Overview...................................................................................... 20 Outline Dimensions ....................................................................... 26 Preamplifier ................................................................................. 20 Ordering Guide .......................................................................... 26 REVISION HISTORY 5/11--Rev. B to Rev. C Change to Figure 2 and Table 3 ...................................................... 6 4/11--Rev. A to Rev. B Change to Table 2 ............................................................................. 5 Changes to Figure 77 and Preamplifier Section ......................... 20 Changes to Evaluation Board Section, Optional Circuitry Section, and Board Layout Considerations Section................... 24 Added Table 6.................................................................................. 24 Deleted Figure 83; Renumbered Figures Sequentially............... 24 Changes to Figure 82, Figure 83, and Figure 84 ......................... 24 Changes to Figure 85, Figure 86, Figure 87, and Figure 88 ....... 25 Deleted Table 6 ................................................................................ 26 9/08--Rev. 0 to Rev. A Change to General Description Section .........................................1 Deleted Input Capacitance Parameter, Table 1 ..............................3 Added Exposed Pad Notation to Figure 2......................................6 Changes to Figure 11.........................................................................8 Changes to Figure 55...................................................................... 15 Change to Preamplifier Section .................................................... 20 Changes to Noise Section .............................................................. 21 Change to Circuit Configuration for Noninverting Gain Section .................................................................................... 22 Changes to Table 5.......................................................................... 22 Changes to Figure 89 and Table 6................................................. 26 Updated Outline Dimensions ....................................................... 27 Changes to Ordering Guide .......................................................... 27 10/06--Revision 0: Initial Version Rev. C | Page 2 of 28 AD8336 SPECIFICATIONS VS = 5 V, T = 25C, gain range = -14 dB to +46 dB, preamp gain = 4x, f = 1 MHz, CL = 5 pF, RL = 500 , PWRA = GND, unless otherwise specified. Table 1. Parameter PREAMPLIFIER -3 dB Small-Signal Bandwidth -3 dB Large-Signal Bandwidth Bias Current, Either Input Differential Offset Voltage Input Resistance Input Capacitance PREAMPLIFIER + VGA -3 dB Small-Signal Bandwidth -3 dB Large-Signal Bandwidth Slew Rate Short-Circuit Preamp Input Voltage Noise Spectral Density Input Current Noise Spectral Density Output-Referred Noise DYNAMIC PERFORMANCE Harmonic Distortion HD2 HD3 HD2 HD3 Input 1 dB Compression Point Two-Tone Intermodulation Distortion (IMD3) Output Third-Order Intercept Overdrive Recovery Group Delay Variation PrA Gain = 20x Test Conditions/Comments Min Typ Max Unit 1 VOUT = 10 mV p-p VOUT = 2 V p-p 150 85 725 600 900 3 MHz MHz nA V k pF VOUT = 10 mV p-p VOUT = 10 mV p-p, PWRA = 5 V VOUT = 10 mV p-p, PrA gain = 20x VOUT = 10 mV p-p, PrA gain = -3x 115 40 20 125 MHz MHz MHz MHz VOUT = 2 V p-p VOUT = 2 V p-p, PWRA = 5 V VOUT = 2 V p-p, PrA gain = 20x VOUT = 2 V p-p, PrA gain = -3x VOUT = 2 V p-p 3 V VS 12 V 80 30 20 100 550 3.0 MHz MHz MHz MHz V/s nV/Hz VGAIN = 0.7 V, PrA gain = 4x VGAIN = -0.7 V, PrA gain = 4x VGAIN = 0.7 V, PrA gain = 20x VGAIN = -0.7 V, PrA gain = 20x VGAIN = 0.7 V, -55C T +125C VGAIN = -0.7 V, -55C T +125C 3.0 600 190 2500 200 700 250 pA/Hz nV/Hz nV/Hz nV/Hz nV/Hz nV/Hz nV/Hz VGAIN = 0 V, VOUT = 1 V p-p f = 1 MHz f = 1 MHz f = 10 MHz f = 10 MHz VGAIN = -0.7 V VGAIN = +0.7 V VGAIN = 0 V, VOUT = 1 V p-p, f1 = 0.95 MHz, f2 = 1.05 MHz VGAIN = 0 V, VOUT = 1 V p-p, f1 = 9.95 MHz, f2 = 10.05 MHz VGAIN = 0 V, VOUT = 2 V p-p, f1 = 0.95 MHz, f2 = 1.05 MHz VGAIN = 0 V, VOUT = 2 V p-p, f1 = 9.95 MHz, f2 = 10.05 MHz VGAIN = 0 V, VOUT = 1 V p-p, f = 1 MHz VGAIN = 0 V, VOUT = 1 V p-p, f = 10 MHz VGAIN = 0 V, VOUT = 2 V p-p, f = 1 MHz VGAIN = 0 V, VOUT = 2 V p-p, f = 10 MHz VGAIN = 0.7 V, VIN = 100 mV p-p to 5 mV p-p 1 MHz < f < 10 MHz, full gain range 1 MHz < f < 10 MHz, full gain range -58 -68 -60 -60 11 -23 -71 -69 -60 -58 34 32 34 33 50 1 3 dBc dBc dBc dBc dBm dBm dBc dBc dBc dBc dBm dBm dBm dBm ns ns ns Rev. C | Page 3 of 28 AD8336 Parameter ABSOLUTE GAIN ERROR 2 GAIN CONTROL INTERFACE Gain Scaling Factor Intercept Gain Range Input Voltage (VGAIN) Range Input Current Response Time OUTPUT PERFORMANCE Output Impedance, DC to 10 MHz Output Signal Swing Output Current Short-Circuit Current Output Offset Voltage PWRA PIN Normal Power (Logic Low) Low Power (Logic High) Normal Power (Logic Low) Low Power (Logic High) Normal Power (Logic Low) Low Power (Logic High) POWER SUPPLY Supply Voltage Operating Range Quiescent Current VS = 3 V Test Conditions/Comments -0.7 V < VGAIN < -0.6 V -0.6 V < VGAIN < -0.5 V -0.5 V < VGAIN < +0.5 V -0.5 V < VGAIN < +0.5 V, 3 V VS 12 V -0.5 V < VGAIN < +0.5 V, -55C T +125C -0.5 V < VGAIN < +0.5 V, PrA gain = -3x 0.5 V < VGAIN < +0.6 V 0.6 V < VGAIN < +0.7 V 48 49.9 16.4 4.5 60 52 0 0 Unit 1 dB dB dB dB dB dB dB dB 1 300 3 V VS 12 V RL 500 (for |VS| 5 V); RL 1 k above that RL 1 k (for |VS| = 12 V) Linear operation - minimum discernable distortion VS = 3 V VS = 5 V VS = 12 V VGAIN = 0.7 V, gain = 200x 3 V VS 12 V -55C T +125C 2.5 |VS| - 1.5 |VS| - 2.25 20 +123/-72 +123/-72 +72/-73 -125 -200 -200 V V mA mA mA mA mV mV mV VS = 3 V VS = 3 V VS = 5 V VS = 5 V VS = 12 V VS = 12 V -250 62 +VS +150 0.7 1.5 1.2 2.0 3.2 4.0 3 22 VS = 12 V 2 Max 6 3 +1.25 +1.25 60 dB gain change 58 -VS No foldover -55C T +125C PWRA = 5 V 1 Typ 1 to 5 0.5 to 1.5 0.2 0.5 0.5 0.5 -1.5 to -3.0 -1 to -5 dB/V dB dB dB V A ns VS = 5 V PSRR -4.0 -9.0 Preamp + VGA VGA only -55C T +125C PWRA = 3 V Power Dissipation Min 0 0 -1.25 -55C T +125C PWRA = 5 V VS = 3 V VS = 5 V VS = 12 V VGAIN = 0.7 V, f = 1 MHz All dBm values are calculated with 50 reference, unless otherwise noted. Conformance to theoretical gain expression (see the Setting the Gain section). Rev. C | Page 4 of 28 10 22 10 23 12 25 23 to 31 14 26 23 to 31 14 28 24 to 33 16 150 260 672 -40 V V V V V V V 30 mA 18 30 mA 18 31 mA mW mW mW dB AD8336 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage (VPOS, VNEG) Input Voltage (INPP, INPN) Gain Voltage (GPOS, GNEG) PWRA VGAI Power Dissipation VS 5 V 5 V < VS 12 V Operating Temperature Range 3 V < VS 10 V 10 V < VS 12 V Storage Temperature Range Lead Temperature (Soldering 60 sec) Thermal Data 1 JA JB JC JT JB 1 Stresses above those listed under the Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rating 15 V VPOS, VNEG VPOS, VNEG 5 V, GND VPOS + 0.6 V, VNEG - 0.6 V 0.43 W 1.12 W ESD CAUTION -55C to +125C -55C to +85C -65C to +150C 300C 58.2C/W 35.9C/W 9.2C/W 1.1C/W 34.5C/W 4-layer JEDEC board, no airflow, exposed pad soldered to printed circuit board. Rev. C | Page 5 of 28 AD8336 VPOS GNEG PWRA 16 15 14 13 12 PIN 1 INDICATOR 11 2 VCOM 3 10 VNEG AD8336 5 6 7 8 NC PRAO TOP VIEW 4 (Not to Scale) 9 NC INPP 1 INPN VOUT GPOS VGAI NOTES 1. NC = NO CONNECT. 2. THE EXPOSED PAD IS NOT CONNECTED INTERNALLY. FOR INCREASED RELIABILITY OF THE SOLDER JOINTS AND MAXIMUM THERMAL CAPABILITY, IT IS RECOMMENDED THAT THE PADDLE BE SOLDERED TO THE GROUND PLANE. 06228-002 NC NC NC PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Mnemonic VOUT PWRA VCOM INPP INPN NC NC PRAO VGAI VNEG GPOS GNEG VPOS NC NC NC Description Output Voltage. Power Control. Normal power when grounded; power reduced by half if PWRA is pulled high. Common-Mode Voltage. Normally GND when using a dual supply. Positive Input to Preamp. Negative Input to Preamp. No Connect. No Connect. Preamp Output. VGA Input. Negative Supply. Positive Gain Control Input. Negative Gain Control Input. Positive Supply. No Connect. No Connect. No Connect. Rev. C | Page 6 of 28 AD8336 TYPICAL PERFORMANCE CHARACTERISTICS VS = 5 V, T = 25C, gain range = -14 dB to +46 dB, preamp gain = 4x, f = 1 MHz, CL = 5 pF, RL = 500 , PWRA = GND, unless otherwise specified. 50 2.0 T = +125C T = +25C T = -55C 40 1.0 GAIN ERROR (dB) 20 10 0 -0.5 -400 -200 0 200 400 600 800 VGAIN (mV) -2.0 -800 06228-003 -600 Figure 3. Gain vs. VGAIN for Three Values of Temperature (T) (See Figure 56) -400 -200 0 200 VGAIN (mV) 400 600 800 Figure 6. Gain Error vs. VGAIN for Three Values of Temperature (T) (See Figure 56) 50 2.0 VS = 12V VS = 5V VS = 3V 40 -600 06228-006 -1.5 -20 -800 VS = 12V VS = 5V VS = 3V 1.5 1.0 GAIN ERROR (dB) 30 20 10 0 0.5 0 -0.5 -1.0 -10 -1.5 -600 -400 -200 200 0 VGAIN (mV) 400 600 800 -2.0 -800 06228-004 -20 -800 Figure 4. Gain vs. VGAIN for Three Values of Supply Voltage (VS) (See Figure 56) -600 -400 -200 0 200 VGAIN (mV) 400 600 06228-007 GAIN (dB) 0 -1.0 -10 800 Figure 7. Gain Error vs. VGAIN for Three Values of Supply Voltage (VS) (See Figure 56) 70 2.0 60 1.5 50 PREAMP GAIN = 20x PREAMP GAIN = 4x 1.0 GAIN ERROR (dB) 40 GAIN (dB) 0.5 30 PREAMP GAIN = 20x PREAMP GAIN = 4x 10 0.5 0 -0.5 -1.0 0 -1.5 -10 -600 -400 -200 0 200 400 600 VGAIN (mV) 800 -2.0 -800 06228-005 -20 -800 Figure 5. Gain vs. VGAIN for Preamp Gains of 4x and 20x (See Figure 56) -600 -400 -200 0 200 VGAIN (mV) 400 600 800 Figure 8. Gain Error vs. VGAIN for Preamp Gains of 4x and 20x (See Figure 56) Rev. C | Page 7 of 28 06228-008 GAIN (dB) 30 20 T = +125C T = +25C T = -55C 1.5 AD8336 2.0 PREAMP GAIN = PREAMP GAIN = PREAMP GAIN = PREAMP GAIN = 1.5 50 4x, f = 1MHz 4x, f = 10MHz 20x, f = 1MHz 20x, f = 10MHz 60 UNITS VGAIN = -0.3V VGAIN = +0.3V 40 0.5 % OF UNITS GAIN ERROR (dB) 1.0 0 -0.5 30 20 -1.0 10 Figure 9. Gain Error vs. VGAIN at 1 MHz and 10 MHz and for Preamp Gains of 4x and 20x (See Figure 56) 2.0 GAIN ERROR (dB) Figure 12. Gain Error Histogram 50 PREAMP GAIN = -3x, f = 1MHz PREAMP GAIN = -3x, f = 10MHz PREAMP GAIN = -19x, f = 1MHz PREAMP GAIN = -19x, f = 10MHz 1.5 06228-012 0 0.16 800 0.12 600 0.08 400 0.04 0 200 VGAIN (mV) 0 -200 -0.04 -400 -0.08 -600 06228-009 -2.0 -800 -0.12 -1.5 60 UNITS -0.3V VGAIN 0.3V 40 0.5 % OF UNITS GAIN ERROR (dB) 1.0 0 -0.5 30 20 -1.0 10 -1.5 -400 -200 0 200 VGAIN (mV) 400 600 800 0 49.6 49.7 49.8 49.9 50.0 50.1 06228-013 -600 06228-010 -2.0 -800 50.2 GAIN SCALING (dB/V) Figure 10. Gain Error vs. VGAIN at 1 MHz and 10 MHz and for Inverting Preamp Gains of -3x and -19x (See Figure 56) Figure 13. Gain Scaling Factor Histogram 20 50 0 35 0 -5 -10 -15 -15 -10 -5 0 5 10 COMMON-MODE VOLTAGE VGAIN (V) 15 06228-011 GAIN (dB) OUTPUT OFFSET VOLTAGE (mV) VS = 12V VS = 5V VS = 3V 40 Figure 11. Gain vs. Common-Mode Voltage at VGAIN -20 -40 -60 -80 -100 -120 -140 -160 T = +125C T = +85C T = +25C -200 T = -40C T = -55C -220 -0.8 -0.6 -0.4 -180 -0.2 0 0.2 VGAIN (V) 0.4 0.6 Figure 14. Output Offset Voltage vs. VGAIN for Various Values of Temperature (T) Rev. C | Page 8 of 28 0.8 06228-014 45 AD8336 20 50 +0.5V -20 30 -40 GAIN (dB) -60 -80 -100 +0.2V 20 0V 10 -0.2V 0 -120 -0.5V -140 -10 -0.7V -160 -200 -0.8 VS = 12V VS = 5V VS = 3V -0.6 -20 -0.4 -0.2 0 0.2 VGAIN (V) 0.4 0.6 0.8 -30 100k 50 VGAIN = +0.7V +0.5V 40 30 10 +0.2V 20 30 -200 -160 -120 -80 -40 OUTPUT OFFSET (mV) 0 40 GAIN (dB) 0 -240 80 0V 10 -0.2V 0 SAMPLE SIZE = 60 UNITS VGAIN = 0V 20 100M 200M Figure 18. Frequency Response for Various Values of VGAIN (See Figure 57) SAMPLE SIZE = 60 UNITS VGAIN = 0.7V 20 10M FREQUENCY (Hz) Figure 15. Output Offset Voltage vs. VGAIN for Three Values of Supply Voltage (VS) 30 1M 06228-018 -180 % OF UNITS VGAIN = +0.7V 40 06228-015 OUTPUT OFFSET VOLTAGE (mV) 0 -0.5V -10 10 -0.7V -20 -20 -16 -12 -8 -4 OUTPUT OFFSET (mV) 0 4 8 06228-016 -24 1M 10M FREQUENCY (Hz) 100M 200M 06228-019 LOW POWER MODE -30 100k 0 Figure 19. Frequency Response for Various Values of VGAIN, Low Power Mode (See Figure 57) Figure 16. Output Offset Histogram 70 50 60 UNITS 60 40 VGAIN = +0.7V +0.5V GAIN (dB) 20 30 20 10 10 0 16.30 16.35 16.40 16.45 INTERCEPT (dB) 16.50 16.55 0V -0.2V -0.5V -0.7V PREAMP GAIN = 20x -10 100k 1M 0 16.25 +0.2V Figure 17. Intercept Histogram 10M FREQUENCY (Hz) 100M 200M Figure 20. Frequency Response for Various Values of VGAIN When the Preamp Gain is 20x (See Figure 57) Rev. C | Page 9 of 28 06228-020 40 30 06228-017 % OF UNITS 50 AD8336 50 30 VGAIN = +0.7V +0.5V 40 25 30 GAIN = -19x 20 20 15 0V 10 GAIN (dB) GAIN (dB) +0.2V -0.2V GAIN = -3x 10 5 0 -0.5V -10 0 -5 -20 PREAMP GAIN = -3x 1M 10M FREQUENCY (Hz) 100M 200M 1M 10M FREQUENCY (Hz) 100M 500M Figure 24. Preamp Frequency Response for Three Values of Supply Voltage (VS) When the Inverting Gain Value is -3x or -19x (See Figure 69) Figure 21. Frequency Response for Various Values of VGAIN When the Preamp Gain is -3x (See Figure 69 and Figure 57) 25 -10 100k 06228-021 -30 100k VS = 12V VS = 5V VS = 3V 06228-024 -0.7V 20 PREAMP GAIN = 20x PREAMP GAIN = 4x VGAIN = 0V 20 15 GROUP DELAY (ns) 10 5 0 5 47pF 22pF 10pF 0pF -10 100k 1M 10M FREQUENCY (Hz) 100M 200M 0 1M 06228-022 -5 CL = CL = CL = CL = 10 Figure 22. Frequency Response for Various Values of Load Capacitance (CL) (See Figure 57) 10M FREQUENCY (Hz) 100M 06228-025 GAIN (dB) 15 Figure 25. Group Delay vs. Frequency for Preamp Gains of 4x and 20x (See Figure 59) 1k 30 GAIN = 20x 25 100 GAIN = 4x 10 5 0 -10 100k 1 0.1 VS = 12V VS = 5V VS = 3V 1M 10M FREQUENCY (Hz) 100M 500M 06228-023 -5 10 Figure 23. Preamp Frequency Response for Three Values of Supply Voltage (VS) When the Preamp Gain is 4x or 20x (See Figure 58) Rev. C | Page 10 of 28 0.01 100k 1M 10M FREQUENCY (Hz) 100M 500M Figure 26. Output Resistance vs. Frequency of the Preamp (See Figure 61) 06228-026 GAIN (dB) 15 OUTPUT RESISTANCE () 20 AD8336 1k INPUT-REFERRED NOISE (nV/Hz) 1k 10 1 0.1 VS = 12V VS = 5V VS = 3V 100M 500M 1 -800 6 f = 5MHz INPUT-REFERRED NOISE (nV/Hz) 700 600 500 400 300 100 0 -800 -600 -400 0 -200 200 VGAIN (mV) 400 = +125C = +85C = +25C = -40C = -55C 600 800 Figure 28. Output-Referred Noise vs. VGAIN at Various Temperatures (T) (See Figure 62) INPUT-REFERRED NOISE (nV/Hz) 2100 1800 1500 1200 900 -600 -400 -200 0 VGAIN (mV) 200 400 = +125C = +85C = +25C = -40C = -55C 600 800 06228-029 OUTPUT-REFERRED NOISE (nV/Hz) 2400 0 -800 600 800 4 3 2 1 6 300 400 5 f = 5MHz 2700 PREAMP GAIN = 20x T T T T T 0 200 VGAIN (mV) VS = 12V VS = 5V VS = 3V 1M 10M FREQUENCY (Hz) 100M Figure 31. Short-Circuit Input-Referred Noise vs. Frequency at Maximum Gain for Three Values of Supply Voltage (VS) (See Figure 62) 3000 600 -200 VGAIN = 0.7V 0 100k 06228-028 OUTPUT-REFERRED NOISE (nV/Hz) 800 T T T T T -400 Figure 30. Input-Referred Noise vs. VGAIN for Preamp Gains of 4x and 20x (See Figure 62) 900 200 -600 06228-030 10M FREQUENCY (Hz) 06228-031 1M Figure 27. Output Resistance vs. Frequency of the VGA for Three Values of Supply Voltage (VS) (See Figure 61) 1000 10 PREAMP GAIN = 20x 06228-027 0.01 100k PREAMP GAIN = 4x 100 Figure 29. Output-Referred Noise vs. VGAIN at Various Temperatures (T) When the Preamp Gain is 20x (See Figure 62) Rev. C | Page 11 of 28 VGAIN = 0.7V PREAMP GAIN = -3x 5 4 3 2 1 0 100k 1M 10M FREQUENCY (Hz) 100M Figure 32. Short-Circuit Input-Referred Noise vs. Frequency at Maximum Inverting Gain (See Figure 73) 06228-032 OUTPUT RESISTANCE () 100 f = 5MHz AD8336 -40 HARMONIC DISTORTION (dBc) -45 10 INPUT-REFERRED NOISE RS THERMAL NOISE ALONE 100 1k SOURCE RESISTANCE () 10k -50 HD2 -55 HD3 -60 -65 -70 0 Figure 33. Input-Referred Noise vs. Source Resistance (See Figure 72) 70 -20 HARMONIC DISTORTION (dBc) 50 SIMULATED DATA 40 30 50 SOURCE -600 -400 -200 0 200 VGAIN (mV) 400 600 800 Figure 34. Noise Figure vs. VGAIN (See Figure 63) -40 HARMONIC DISTORTION (dBc) HD3 -60 600 800 1.0k 1.2k 1.4k 1.6k 1.8k 2.0k 2.2k LOAD RESISTANCE () 06228-035 -65 400 -50 -60 HD2 @ 1MHz HD2 @ 10MHz HD3 @ 1MHz HD3 @ 10MHz -400 -200 0 200 VGAIN (mV) 400 600 800 HD2 f = 5MHz OUTPUT SWING OF PREAMP LIMITS VGAIN LEVELS -30 HD2 200 -40 -20 -55 0 OUTPUT SWING OF PREAMP LIMITS VGAIN TO 400mV Figure 37. Second and Third Harmonic Distortion vs. VGAIN at 1 MHz and 10 MHz (See Figure 64) -50 -70 50 -30 -80 -600 VOUT = 2V p-p VGAIN = 0V f = 5MHz -45 45 40 Figure 35. Harmonic Distortion vs. Load Resistance (See Figure 64) -40 -50 -60 -70 -80 -600 VOUT = 0.5V p-p VOUT = 1V p-p VOUT = 2V p-p VOUT = 4V p-p -400 -200 0 200 VGAIN (mV) 400 600 Figure 38. Second Harmonic Distortion vs. VGAIN for Four Values of Output Voltage (VOUT) (See Figure 64) Rev. C | Page 12 of 28 800 06228-038 0 -800 15 20 25 30 35 LOAD CAPACITANCE (pF) VOUT = 1V p-p -70 UNTERMINATED 06228-034 NOISE FIGURE (dB) 60 10 10 Figure 36. Harmonic Distortion vs. Load Capacitance (See Figure 64) f = 10MHz 20 5 06228-037 1 0.1 10 HARMONIC DISTORTION (dBc) VOUT = 2V p-p VGAIN = 0V f = 5MHz 06228-036 VGAIN = 0.7V 06228-033 INPUT-REFERRED NOISE (nV/Hz) 100 AD8336 HD3 f = 5MHz 40 OUTPUT SWING OF PREAMP LIMITS MINIMUM USABLE VGAIN LEVELS 1MHz 500mV 1MHz 1V 10MHz 500mV 10MHz 1V 35 -30 OUTPUT IP3 (dBm) 30 -40 -50 -60 25 20 15 10 -80 -600 VOUT VOUT VOUT VOUT = 0.5V p-p = 1V p-p = 2V p-p = 4V p-p -400 -200 5 400 0 200 VGAIN (mV) 600 800 VOUT = 1V p-p VGAIN = 0V COMPOSITE INPUTS SEPARATED BY 100kHz 0 -800 Figure 39. Third Harmonic Distortion vs. VGAIN for Four Values of Output Voltage (VOUT) (See Figure 64) -400 200 -200 0 VGAIN (mV) 400 600 800 Figure 42. Output-Referred IP3 (OIP3) vs. VGAIN at Two Frequencies and Two Input Levels (see Figure 76) 30 VOUT = 2V p-p VGAIN = 0V INPUT LEVEL LIMITED BY GAIN OF PREAMP VS = 12V 20 -30 VS = 5V 10 IP1dB (dBm) HARMONIC DISTORTION (dBc) -20 -600 06228-042 -70 06228-039 HARMONIC DISTORTION (dBc) -20 -40 HD2 -50 VS = 3V 0 -10 -60 -20 10M FREQUENCY (Hz) 50M -10 -600 -400 -200 200 0 VGAIN (mV) 400 600 800 Figure 43. Input P1dB (IP1dB) vs. VGAIN at Three Power Supply Values (VS) (see Figure 74 and Figure 75) Figure 40. Harmonic Distortion vs. Frequency (See Figure 64) 0 -30 -800 06228-040 -70 1M 06228-043 HD3 3 VOUT = 1V p-p VGAIN = 0V TONES SEPARATED BY 100kHz 2 -20 VOLTAGE (V) 1 -40 -50 -60 0 VIN (V) VOUT (V) -1 -70 -2 -90 1M 10M FREQUENCY (Hz) 100M -3 -100 0 100 TIME (ns) 200 300 Figure 44. Large-Signal Pulse Response of the Preamp (See Figure 65) Figure 41. IMD3 vs. Frequency (see Figure 76) Rev. C | Page 13 of 28 06228-044 -80 06228-041 IMD3 (dBc) -30 AD8336 0 -0.2 VIN (mV) VOUT (mV) 0 -20 -0.4 0 50 100 150 TIME (ns) 200 250 300 -60 350 0.5 0 -5 -0.5 -1.5 -20 -2.0 -25 -100 20 50 250 300 -2.5 350 2.0 1.5 1.0 5 0.5 0 0 INPUT -10 -0.4 -40 -15 0 50 100 150 TIME (ns) 200 250 300 -60 350 -20 -100 2.5 VGAIN = 0.7V 1.0 5 0.5 0 0 -5 -0.5 -10 -1.0 -50 0 50 100 150 TIME (ns) 200 100 150 200 TIME (ns) 250 300 350 VOUT (V) -2.0 400 3 VGAIN = 0.7V VS = 5V 2 10 1 0 0 -20 INPUT CL = 0pF CL = 10pF CL = 22pF CL = 47pF* -1 -2 -2.0 250 300 -2.5 350 06228-047 -25 -100 50 20 -10 -1.5 INPUT OUTPUT WHEN PWRA = 0 OUTPUT WHEN PWRA = 1 -20 VIN (mV) 10 VOUT (mV) 1.5 -15 30 2.0 15 0 -1.5 Figure 49. Large-Signal Pulse Response for Various Values of Load Capacitance Using 3 V Power Supplies (See Figure 65) Figure 46. Inverting Gain Small-Signal Pulse Response (See Figure 70) 25 -50 -1.0 *WITH 20 RESISTOR IN SERIES WITH OUTPUT. -30 -100 -50 0 50 100 150 200 250 TIME (ns) Figure 47. Large-Signal Pulse Response for Both Power Levels (See Figure 65) 300 -3 350 Figure 50. Large-Signal Pulse Response for Various Values of Load Capacitance Using 5 V Power Supplies (See Figure 65) Rev. C | Page 14 of 28 06228-050 -50 06228-046 -0.6 -100 -0.5 INPUT CL = 0pF CL = 10pF CL = 22pF CL = 47pF 06228-049 -5 -20 VOUT (mV) 0 -0.2 VIN (mV) 200 10 VIN (mV) 0 20 100 150 TIME (ns) 20 VOUT (mV) VIN (mV) 0 VGAIN = 0.7V VS= 3V 15 40 0.2 -50 Figure 48. Inverting Gain Large-Signal Pulse Response (See Figure 70) 60 VGAIN = 0.7V PREAMP GAIN = -3x -1.0 INPUT -15 OUTPUT 0.4 1.0 5 Figure 45. Noninverting Small-Signal Pulse Response for Both Power Levels (See Figure 65) 0.6 1.5 0 -10 -40 INPUT OUTPUT WHEN PWRA = 0 OUTPUT WHEN PWRA = 1 2.0 VGAIN = 0.7V PREAMP GAIN = -3x 10 20 06228-045 VIN (mV) 0.2 15 VOUT (mV) 40 -50 OUTPUT 20 0.4 -0.6 -100 2.5 25 60 VGAIN = 0.7V 06228-048 0.6 AD8336 3 10 20 2 0 10 1 0 0 50 -30 -2 100 150 TIME (ns) 200 250 300 -50 -3 350 -60 100k Figure 51. Large-Signal Pulse Response for Various Values of Load Capacitance Using 12 V Power Supplies (See Figure 65) VOLTAGE (V) 0.5 VOUT VGAIN -0.5 -2.5 -0.5 0 0.5 1.0 TIME (s) 1.5 2.0 06228-052 -1.5 4 0.3 3 0.2 2 0.1 1 0 0 -0.1 -1 -0.2 -2 -0.3 OUTPUT VOLTAGE (V) 5 VGAIN = 0.7V 0.4 -3 VIN (V) VOUT (V) -4 -5 -6 -3 0 3 TIME (s) 6 06228-053 -0.5 -9 20 LOW POWER 10 VS = 12V VS = 5V VS = 3V 0 -65 -45 -25 -5 15 35 55 75 TEMPERATURE (C) 95 115 135 Figure 55. IQ vs. Temperature for Three Values of Supply Voltage and High and Low Power (See Figure 68) Figure 52. Gain Response (See Figure 66) -0.4 HIGH POWER 30 Figure 53. VGA Overdrive Recovery (See Figure 67) Rev. C | Page 15 of 28 06228-055 QUIESCENT SUPPLY CURRENT (mA) 40 1.5 INPUT VOLTAGE (V) 5M Figure 54. PSRR vs. Frequency for Three Values of VGAIN (See Figure 71) 2.5 0.5 1M FREQUENCY (Hz) 06228-054 0 -20 -40 *WITH 20 RESISTOR IN SERIES WITH OUTPUT -50 VGAIN = 0.7V VGAIN = 0V VGAIN = -0.7V -1 -20 -30 -100 PSRR (dB) INPUT CL = 0pF CL = 10pF* CL = 22pF* CL = 47pF* -10 PSRR VPOS VNEG -10 VOUT (mV) VGAIN = 0.7V VS = 12V 06228-051 VIN (mV) 30 AD8336 TEST CIRCUITS NETWORK ANALYZER NETWORK ANALYZER OUT OUT IN 50 IN 50 50 AD8336 5 1 49.9 8 9 12 4 + 5 - PrA 11 1 8 301 453 9 12 11 301 06228-056 VGAIN 100 06228-059 49.9 AD8336 453 + PrA - 4 50 100 Figure 56. Gain vs. VGAIN and Gain Error vs. VGAIN Figure 59. Group Delay NETWORK ANALYZER OUT IN 50 50 453 AD8336 49.9 4 + 5 - AD8336 + PrA - 4 PrA 1 5 1 453 50 DMM 12 11 OPTIONAL CL 301 NETWORK ANALYZER 5 - 50 0 453 NC 4 1 8 9 AD8336 NC PrA 301 CONFIGURE TO MEASURE Z-CONVERTED S22 IN 50 AD8336 + + Figure 60. Offset Voltage IN 50 4 11 NETWORK ANALYZER 49.9 12 100 Figure 57. Frequency Response OUT 9 301 06228-057 VGAIN 100 8 06228-060 8 12 49.9 5 + PrA - 11 1 8 NC 12 11 301 453 100 100 06228-058 NC = NO CONNECT 9 0 NC NC = NO CONNECT Figure 61. Output Resistance vs. Frequency Figure 58. Frequency Response of the Preamp Rev. C | Page 16 of 28 06228-061 5 AD8336 OSCILLOSCOPE PULSE GENERATOR SPECTRUM ANALYZER POWER SPLITTER OUT CH2 CH1 IN 50 50 50 AD8336 AD8336 + PrA - 4 5 1 OPTIONAL 20 453 + PrA - 4 5 1 49.9 8 8 9 12 11 12 11 0.7V 06228-065 100 06228-062 VGAIN 100 9 301 301 Figure 62. Input-Referred Noise and Output-Referred Noise Figure 65. Pulse Response OSCILLOSCOPE PULSE FUNCTION GENERATOR GENERATOR NOISE FIGURE METER NOISE SOURCE DRIVE SINE WAVE SQUARE WAVE 50 DIFFERENTIAL FET PROBE 11 AD8336 0 1 49.9 453 + PrA - 4 + PrA - 5 50 0 AD8336 49.9 (OR ) CH2 CH1 INPUT NOISE SOURCE 4 POWER SPLITTER 5 8 8 9 12 NC 1 9 12 301 11 301 06228-063 06228-066 100 VGAIN 100 NC = NO CONNECT Figure 66. Gain Response Figure 63. Noise Figure vs. VGAIN OSCILLOSCOPE ARBITRARY WAVEFORM GENERATOR SPECTRUM ANALYZER RL INPUT SIGNAL GENERATOR -20dB 50 LOW-PASS FILTER 1 NC 1 CL 8 9 12 8 301 11 301 100 5 9 12 11 0.7V 100 VGAIN 06228-067 5 50 453 + PrA - 4 49.9 + PrA - 06228-064 49.9 CH2 50 AD8336 AD8336 4 CH1 POWER SPLITTER NC = NO CONNECT Figure 64. Harmonic Distortion Figure 67. VGA Overdrive Recovery Rev. C | Page 17 of 28 AD8336 POWER SUPPLIES CONNECTED TO NETWORK ANALYZER BIAS PORT NETWORK ANALYZER BENCH POWER SUPPLY DMM (+I) OUT IN 50 13 AD8336 4 + 5 - PrA BYPASS CAPACITORS REMOVED FOR MEASUREMENT 1 VPOS OR VNEG AD8336 + PrA - 4 49.9 8 9 50 12 11 5 1 10 DIFFERENTIAL FET PROBE 301 8 DMM (-I) 9 12 11 06228-068 301 VGAIN 100 Figure 68. Supply Current 06228-071 100 Figure 71. Power Supply Rejection Ratio NETWORK ANALYZER SPECTRUM ANALYZER OUT IN 50 IN 50 50 453 AD8336 4 100 PrA - 5 + PrA - 4 1 5 1 49.9 8 9 12 8 11 9 12 11 301 VGAIN 06228-069 301 0.7V 100 06228-072 100 AD8336 + Figure 72. Input-Referred Noise vs. Source Resistance Figure 69. Frequency Response, Inverting Gain SPECTRUM ANALYZER PULSE GENERATOR OSCILLOSCOPE POWER SPLITTER OUT IN CH2 CH1 50 50 50 AD8336 AD8336 100 5 - 4 PrA 1 453 5 + PrA - 49.9 1 8 8 301 9 12 0.7V 9 12 11 301 11 06228-070 100 + 100 0.7V 06228-073 4 Figure 73. Short-Circuit Input-Referred Noise vs. Frequency Figure 70. Pulse Response, Inverting Gain Rev. C | Page 18 of 28 AD8336 SPECTRUM ANALYZER SIGNAL GENERATOR IN OUT 50 50 OPTIONAL 20dB ATTENUATOR 22dB AD8336 453 4 + 5 - PrA 49.9 1 8 9 12 11 301 06228-074 VGAIN 100 Figure 74. IP1dB vs. VGAIN SPECTRUM ANALYZER SIGNAL GENERATOR OUT IN 50 50 -20dB AD8336 AMPLIFIER 49.9 5 + PrA - 4 1 5 8 9 12 453 + - PrA 11 301 1 8 9 12 11 301 0.7V 100 VGAIN 100 06228-075 4 AD8336 DUT 0 Figure 75. IP1dB vs. VGAIN, High Signal Level Inputs SPECTRUM ANALYZER INPUT 50 +22dB -6dB SIGNAL GENERATOR COMBINER -6dB +22dB -6dB AD8336 DUT 49.9 4 + 5 - 453 PrA 1 SIGNAL GENERATOR 8 9 12 11 100 Figure 76. IMD and OIP3 Rev. C | Page 19 of 28 VGAIN 06228-076 301 AD8336 THEORY OF OPERATION OVERVIEW PREAMPLIFIER The AD8336 is the first VGA designed for operation over exceptionally broad ranges of temperature and supply voltage. Its performance has been characterized from temperatures extending from -55C to +125C, and supply voltages from 3 V to 12 V. It is ideal for applications requiring dc coupling, large output voltage swings, very large gain ranges, extreme temperature variations, or a combination thereof. The gain of the uncommitted voltage feedback preamplifier is set with external resistors. The combined preamplifier and VGA gain is specified in two ranges: -14 dB to +46 dB and 0 dB to 60 dB. Since the VGA gain is fixed at 34 dB (50x), the preamp gain is adjusted for gains of 12 dB (4x) and 26 dB (200x). The simplified block diagram is shown in Figure 77. The AD8336 includes a voltage feedback preamplifier, an amplifier with a fixed gain of 34 dB, a 60 dB attenuator, and various bias and interface circuitry. The independent voltage feedback op amp can be used in noninverting and inverting configurations and functions as a preamplifier to the variable gain amplifier (VGA). If desired, the op amp output (PRAO) and VGA input (VGAI) pins provide for connection of an interstage filter to eliminate noise and offset. The bandwidth of the AD8336 is dc to 100 MHz with a gain range of 60 dB (-14 dB to +46 dB). For applications that require large supply voltages, a reduction in power is advantageous. The power reduction pin (PWRA) permits the power and bandwidth to be reduced by about half in such applications. PRAO VGAI 12dB INPP + INPN * PrA - RFB2 301 34dB -60dB TO 0dB ATTENUATOR AND GAIN 1.28k CONTROL INTERFACE + _ VOUT 4.48k 91.43 RFB1 100 Typical of voltage feedback amplifier configurations, the gainbandwidth product of the AD8336 is fixed (at 600); therefore, the bandwidth decreases as the gain is increased beyond the nominal gain value of 4x. For example, if the preamp gain is increased to 20x, the bandwidth reduces by a factor of 5 to about 20 MHz. The -3 dB bandwidth of the preamplifier with a gain of 4x is about 150 MHz, and for the 20x gain is about 30 MHz. The preamp gain diminishes for an amplifier configured for inverting gain, using the same value of feedback resistors as for a noninverting amplifier, but the bandwidth remains unchanged. For example, if the noninverting gain is 4x, the inverting gain is -3x, but the bandwidth stays the same as in the noninverting gain of 4x. However, because the output-referred noise of the preamplifier is the same in both cases, the input-referred noise increases as the ratio of the two gain values increases. For the previous example, the input-referred noise increases by a factor of 4/3. The output swing of the preamplifier is the same as for the VGA. GPOS GNEG VCOM *OPTIONAL DEPEAKING CAPACITOR. SEE TEXT. 06228-077 BIAS PWRA VPOS VNEG With low preamplifier gains between 2x and 4x, it may be desirable to reduce the high frequency gain with a shunt capacitor across RFB2 to ameliorate peaking in the frequency domain (see Figure 77). To maintain stability, the gain of the preamplifier must be 6 dB (2x) or greater. Figure 77. Simplified Block Diagram To maintain low noise, the output stages of both the preamplifier and the VGA are capable of driving relatively small load resistances. However, at the largest supply voltages, the signal current may exceed safe operating limits for the amplifiers and, therefore, the load current must not exceed 50 mA. With a 12 V supply and 10 V output voltage at the preamplifier or VGA output, load resistances as low as 200 are acceptable. For power supply voltages 10 V, the maximum operating temperature range is derated to +85C because the power may exceed safe limits (see the Absolute Maximum Ratings section). Because harmonic distortion products may increase for various combinations of low impedance loads and high output voltage swings, it is recommended that the user determine load and drive conditions empirically. VGA The architecture of the variable gain amplifier (VGA) section of the AD8336 is based on the Analog Devices, Inc., X-AMP (exponential amplifier), found in a wide variety of Analog Devices variable gain amplifiers. This type of VGA combines a ladder attenuator and interpolator, followed by a fixed-gain amplifier. The gain control interface is fully differential, permitting positive or negative gain slopes. Note that the common-mode voltage of the gain control inputs increases with increasing supply. The gain slope is 50 dB/V and the intercept is 16.4 dB when the nominal preamp gain is 4x (12 dB). The intercept changes with the preamp gain; for example, when the preamp gain is set to 20x (26 dB), the intercept becomes 30.4 dB. Pin VGAI is connected to the input of the ladder attenuator. The ladder ratio is R/2R and the nominal resistance is 320 . To reduce preamp loading and large-signal dissipation, the input resistance at Pin VGAI is 1.28 k. Safe current density and power dissipation levels are maintained even when large dc signals are applied to the ladder. The tap resistance of the resistors within the R/2R ladder is 640 /3, or 213.3 , and is the Johnson noise source of the attenuator. Rev. C | Page 20 of 28 AD8336 SETTING THE GAIN NOISE The overall gain of the AD8336 is the sum (in decibels) or the product (magnitude) of the preamp gain and the VGA gain. The preamp gain is calculated as with any op amp, as seen in the Applications Information section. It is most convenient to think of the device gain in exponential terms (that is, in decibels) since the VGA responds linearly in decibels with changes in control voltage VGAIN at the gain pins. The noise of the AD8336 is dependent on the value of the VGA gain. At maximum VGAIN, the dominant noise source is the preamp, but it shifts to the VGA as VGAIN diminishes. The gain equation for the VGA is Table 4. AD8336 Noise Components for Preamp Gain = 4x 50 dB + 4. 4 dB VGA Gain (dB) = V GAIN (V) x V where VGAIN = VGPOS - VGNEG. The gain and gain range of the VGA are both fixed at 34 dB and 60 dB, respectively; thus, the composite device gain is changed by adjusting the preamp gain. For a preamp gain of 12 dB (4x), the composite gain is -14 dB to +46 dB. Therefore, the calculation for the composite gain (in decibels) is Composite Gain = GPRA + [VGAIN (V) x 49.9 dB/V] + 4.4 dB For example, the midpoint gain when the preamp gain is 12 dB is 12 dB + [0 V x 49.9 dB/V] + 4.4 dB = 16.4 dB Figure 3 is a plot of gain in decibels vs. VGAIN in millivolts, when the preamp gain is 12 dB (4x). Note that the computed result closely matches the plot of actual gain. In Figure 3, the gain slope flattens at the limits of the VGAIN input. The gain response is linear-in-dB over the center 80% of the control range of the device. Figure 78 shows the ideal gain characteristics for the VGA stage gain, the composite gain, and the preamp gain. 70 60 GAIN CHARACTERISTICS COMPOSITE GAIN VGA STAGE GAIN 50 GAIN (dB) 40 30 Noise Component Op Amp (Gain = 4x) RFB1 = 100 RFB2 = 301 VGA Noise Voltage (nV/Hz) 2.6 0.96 0.55 0.77 Using the values listed in Table 4, the total noise of the AD8336 is slightly less than 3 nV/Hz, referred to the input. Although the input noise referred to the VGA is 3.1 nV/Hz, the inputreferred noise at the preamp is 0.77 nV/Hz when divided by the preamplifier gain of 4x. At other than maximum gain, the noise of the VGA is determined from the output noise. The noise in the center of the gain range is about 150 nV/Hz. Because the gain of the fixed-gain amplifier that is part of the VGA is 50x, the VGA input-referred noise is approximately 3 nV/Hz, the same value as the preamp and VGA combined. This is expected since the input-referred noise is the same at the input of the attenuator at maximum gain. However, the noise referred to the VGAI pin (the preamp output) increases by the amount of attenuation through the ladder network. The noise at any point along the ladder network is primarily composed of the ladder resistance noise, the noise of the input devices, and the feedback resistor network noise. The ladder network and the input devices are the largest noise sources. At minimum gain, the output noise increases slightly to about 180 nV/Hz because of the finite structure of the X-AMP. FOR PREAMP GAIN = 26dB USABLE GAIN RANGE OF AD8336 OFFSET VOLTAGE 20 10 0 FOR PREAMP GAIN = 12dB -10 FOR PREAMP GAIN = 6dB -0.5 -0.3 -0.1 0.1 VGAIN (V) 0.3 0.5 Figure 78. Ideal Gain Characteristics of the AD8336 0.7 06228-078 -20 -30 -0.7 The input-referred noise at the highest VGA gain and a preamp gain of 4x, with RFB1 = 100 and RFB2 = 301 , is 3 nV/Hz and is determined by the preamp and its gain setting resistors. See Table 4 for the noise components for the preamp. Extensive cancellation circuitry included in the variable gain amplifier section minimizes locally generated offset voltages. However, when operated at very large values of gain, dc voltage errors at the output can still result from small dc input voltages. When configured for the nominal gain range of -14 dB to +46 dB, the maximum gain is 200x and an offset of only 100 V at the input generates 20 mV at the output. The primary source for dc offset errors is the preamplifier; ac coupling between the PRAO and VGAI pins is the simplest solution. In applications where dc coupling is essential, a compensating current can be injected at the INPN input (Pin 5) to cancel preamp offset. The direction of the compensating current depends on the polarity of the offset voltage. Rev. C | Page 21 of 28 AD8336 APPLICATIONS INFORMATION AMPLIFIER CONFIGURATION Circuit Configuration for Noninverting Gain The AD8336 amplifiers can be configured in various options. In addition to the 60 dB gain range variable gain stage, an uncommitted voltage gain amplifier is available to the user as a preamplifier. The preamplifier connections are separate to enable noninverting or inverting gain configurations or the use of interstage filtering. The AD8336 can be used as a cascade connected VGA with preamp input, as a standalone VGA, or as a standalone preamplifier. This section describes some of the possible applications. The noninverting configuration is shown in Figure 80. The preamp gain is described by the classical op amp gain equation: INPN 5 + PrA - VGAI 8 9 ATTENUATOR -60dB TO 0dB 34dB 1 VOUT R FB 2 The practical gain limits for this amplifier are 6 dB to 26 dB. The gain bandwidth product is about 600 MHz, so at 150 MHz, the maximum achievable gain is 12 dB (4x). The minimum gain is established internally by fixed loop compensation and is 6 dB (2x). This amplifier is not designed for unity-gain operation. Table 5 shows the gain and bandwidth for the noninverting gain configuration. AD8336 INPP INPN PWRA 2 RFB1 100 GAIN CONTROL INTERFACE BIAS +1 R FB1 AD8336 4 5 RFB2 301 8 GAIN = 12dB 13 3 11 12 VNEG VPOS VCOM GPOS GNEG While observing just a few constraints, the uncommitted voltage feedback preamplifier of the AD8336 can be connected in a variety of standard high frequency op amp configurations. The amplifier is optimized for a gain of 4x (12 dB) and has a gain bandwidth product of 600 MHz. At a gain of 4x, the bandwidth is 150 MHz. The preamplifier gain can be adjusted to a minimum gain of 2x; however, there will be a small peak in the response at high frequencies. At higher preamplifier gains, the bandwidth diminishes proportionally in conformance to the classical voltage gain amplifier GBW relationship. While setting the overall gain of the AD8336, the user needs to consider the input-referred offset voltage of the preamplifier. Although the offset of the attenuator and postamplifier are almost negligible, the preamplifier offset voltage, if uncorrected, is increased by the combined gain of the preamplifier and postamplifier. Therefore, for a maximum gain of 60 dB, an input offset voltage of only 200 V results in an error of 200 mV at the output. 34dB 1 VOUT PRAO PWRA VNEG VCOM VPOS VGAI 2 10 -5V 3 13 +5V Figure 80. Circuit Configuration for Noninverting Gain Figure 79. Application Block Diagram PREAMPLIFIER -60dB TO 0dB 9 06228-079 10 PREAMPLIFIER 06228-080 INPP 4 PRAO Gain = The preamplifier output reliably sources and sinks currents up to 50 mA. When using 5 V power supplies, the suggested sum of the output resistor values is 400 total for the optimal tradeoff between distortion and noise. Much of the low gain value device characterization was performed with resistor values of 301 and 100 , resulting in a preamplifier gain of 12 dB (4x). With supply voltages between 5 V and 12 V, the sum of the output resistance should be increased accordingly; a total resistance of 1 k is recommended. Larger resistance values, subject to a trade-off in higher noise performance, can be used if circuit power and load driving is an issue. When considering the total power dissipation, remember that the input ladder resistance of the VGA is part of the preamp load. Table 5. Gain and Bandwidth for Noninverting Preamplifier Configuration Preamp Gain Numerical dB 4x 12 8x 18 16x 24 20x 26 Rev. C | Page 22 of 28 Preamp BW (MHz) 150 60 30 25 Composite Gain (dB) -14 to +46 -8 to +52 -2 to +58 0 to +60 AD8336 Circuit Configuration for Inverting Gain USING THE POWER ADJUST FEATURE The preamplifier can also be used in an inverting configuration, as shown in Figure 81. The AD8336 has the provision to operate at lower power with a trade-off in bandwidth. The power reduction applies to the preamp and the VGA sections, and the bandwidth is reduced equally between them. Reducing the power is particularly useful when operating with higher supply voltages and lower values of output loading that would otherwise stress the output amplifiers. When Pin PWRA is grounded, the amplifiers operate in their default mode, and the combined 3 dB bandwidth is 80 MHz with the preamp gain adjusted to 4x. When the voltage on Pin PWRA is between 1.2 V and 5 V, the power is reduced by approximately half and the 3 dB bandwidth reduces to approximately 35 MHz. The voltage at Pin PWRA must not exceed 5 V. AD8336 GAIN = 9.6dB INPN RFB1 100 RFB2 301 PREAMPLIFIER 4 + 5 - -60dB TO 0dB 8 34dB 1 VOUT PRAO VGAI PWRA VNEG VCOM VPOS 9 2 10 -5V 3 13 +5V 06228-081 INPP Figure 81. Circuit Configuration for Inverting Gain The considerations regarding total resistance vs. distortion, noise, and power that were noted in the noninverting case also apply in the inverting case, except that the amplifier can be operated at unity inverting gain. The signal gain is reduced while the noise gain is the same as for the noninverting configuration: Signal Gain = RFB2 RFB1 and Noise Gain = RFB2 +1 RFB1 DRIVING CAPACITIVE LOADS The output stages of the AD8336 are stable with capacitive loads up to 47 pF for a supply voltage of 3 V and with capacitive loads up to 10 pF for supply voltages up to 8 V. For larger combined values of load capacitance and/or supply voltage, a 20 series resistor is recommended for stability. The influence of capacitance and supply voltage are shown in Figure 50 and Figure 51, where representative combinations of load capacitance and supply voltage requiring a 20 resistor are marked with an asterisk. No resistor is required for the 3 V plots in Figure 49, but a resistor is required for most of the 12 V plots in Figure 51. Rev. C | Page 23 of 28 AD8336 EVALUATION BOARD An evaluation board, AD8336-EVALZ, is available online for the AD8336. Figure 82 is a photo of the board. The board is shipped from the factory configured for a noninverting preamp gain of 4x. To change the value of the gain of the preamp or to change the gain polarity to inverting, alter the component values or install components in the alternate locations provided. All components are standard 0603 size, and the board is compliant with RoHS requirements. Table 6 shows the components to be removed and added to change the amplifier configuration to inverting gain. Remove R4, R7 06228-083 Table 6. Component Changes for Inverting Configuration Install R5, R6 Figure 82. AD8336 Evaluation Board OPTIONAL CIRCUITRY 06228-084 The AD8336 features differential inputs for the gain control, permitting nonzero or floating gain control inputs. To avoid any delay in making the board operational, the gain input circuit is shipped with Pin GNEG connected to ground via a 0 resistor in the R17 location. The user can adjust the gain of the device by driving the GPOS test loop with a power supply or voltage reference. Optional resistor networks R15/R17 and R13/R14 provide fixed-gain bias voltages at Pin GNEG and Pin GPOS for non-zero common-mode voltages. The gain control can also be driven with an active input such as a ramp. Provision is made for an optional SMA connector at PRVG for monitoring the preamp output or for driving the VGA from an external source. Remove the 0 resistor at R9 to isolate the preamp from an external generator. The capacitor at Location C1 limits the bandwidth of the preamplifier. Figure 83. Component Side Copper BOARD LAYOUT CONSIDERATIONS 06228-085 The evaluation board uses four layers, with power and ground planes located between two conductor layers. This arrangement is highly recommended for customers, and several views of the board are provided as reference for board layout details. When laying out a printed circuit board for the AD8336, remember to provide a pad beneath the device to solder the exposed pad of the matching device. The pad in the board should have at least five vias to provide a thermal path for the chip scale package. Unlike leaded devices, the thermal pad is the primary means to remove heat dissipated within the device. Figure 84. Secondary Side Copper Rev. C | Page 24 of 28 06228-088 06228-086 AD8336 Figure 87. Internal Power Plane Copper 06228-087 Figure 85. Component Side Silkscreen Figure 86. Internal Ground Plane Copper VPOS GND GND1 GND2 GND3 + L2 120nH R1 0 VOUT VOUTL VP R16 4.99k CR1 5.1V 16 15 14 13 NC NC NC VPOS 1 LOW R3 0 VIN R2 49.9 C3 0.1F VOUTD C8 0.1F NORM VIN1 R5 VP VOUT 3 R4 0 R6 4 VCOM C6 1nF GNEG U1 POWER 2 PWRA AD8336 GPOS VNEG INPP VGAI GNEG R17 0 12 R14 11 C5 9 0.1F R11 0 R9 0 GPOS C7 1nF 10 INPN NC NC PRAO 5 6 7 8 R8 301 R15 R13 L1 120nH + R12 0 C2 10F 25V -VS PRVG R10 49.9 R7 100 C1 NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. Figure 88. AD8336-EVALZ Schematic Shown as Shipped, Configured for a Noninverting Gain of 4x Rev. C | Page 25 of 28 06228-082 C4 10F 35V AD8336 OUTLINE DIMENSIONS 4.00 BSC SQ 12 MAX 1.00 0.85 0.80 0.65 BSC TOP VIEW 3.75 BSC SQ 0.75 0.60 0.50 0.80 MAX 0.65 TYP 0.35 0.30 0.25 16 13 12 9 PIN 1 INDICATOR 1 2.25 2.10 SQ 1.95 8 5 4 0.25 MIN 1.95 BSC 0.05 MAX 0.02 NOM SEATING PLANE (BOTTOM VIEW) 0.20 REF COPLANARITY 0.08 FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. COMPLIANT TO JEDEC STANDARDS MO-220-VGGC 072808-A PIN 1 INDICATOR 0.60 MAX 0.60 MAX Figure 89. 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 4 mm x 4 mm Body, Very Thin Quad (CP-16-4) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD8336ACPZ-R7 AD8336ACPZ-RL AD8336ACPZ-WP AD8336-EVALZ 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C Package Description 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ] Evaluation Board Z = RoHS Compliant Part. Rev. C | Page 26 of 28 Package Option CP-16-4 CP-16-4 CP-16-4 AD8336 NOTES Rev. C | Page 27 of 28 AD8336 NOTES (c)2006-2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06228-0-5/11(C) Rev. C | Page 28 of 28 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Analog Devices Inc.: AD8336ACPZ-R7 AD8336ACPZ-RL AD8336ACPZ-WP AD8336-EVALZ