Models 152 & 155 Operational Amplifiers Description The Model 152 is an economical, general purpose operational amplifier featuring very low input bias current and high input impedance. It is designed for applications involving high source resistances. The Model 155 has all these same features but is better suited for applications requiring low voltage drift. A versatile circuit building kit, the Model MK150, is available. It makes it easy to connect an amplifier in a wide variety of standard op-amp circuits. These include inverting and noninverting amplifier, integrator, summer, etc. A potentiometer for nulling the input offset and test jacks are provided. Inverting/Filter Amplifier Inverting Summing Amplifier The basic inverting amplifier shown in Figure 1 is useful where a signal inversion or a simple low/high pass filter function is required. The basic inverting amplifiers are used where high slew rate and or high linearity is needed. Figure 2 shows the basic inverting summing amplifier configuration. This amplifier provides the function of summing inputs and providing gain. The summed output can be low pass filtered to reduce high frequency noise if required. Basic Design Equations: Basic Design Equations: GAIN ........................... G = R6 / (R1 + R14) GAIN ........................... G1 = R6/(R1 +R14) Input to Pin H 0.1 < G < 100 G2 = R6/R2 Input to Pin K R6 + RLoad > 2 kohms G3 = R6/R3 Input to Pin L Either R1 or R14 can be zero ohms (jumper) for convenience G4= R6/R4 Input to Pin M 0.1 < G < 100 for any input INPUT IMPEDANCE ... Zin = R1 +R14 R6 || RLoad > 2k ohms BANDWIDTH .............. bw = 3 MHz/(1+G) in Hz Either R1 or R14 can be zero ohms (jumper) for convenience. Value For R5 ............... R5 = Zin || R6 INPUT IMPEDANCE ... Zin = (R1 +R14) or R2 or R3 or R4 For a low pass filter function add C2 by the following equation, Fc = 1 / (2 x pi x R6 x C2) 100 pF < C2 < 1 F BANDWIDTH .............. bw = 3 MHz/(1+R6/Zin) in Hz Value For R5 ............... R5 = Zin ll R6 A FIGURE 1. Inverting Amplifier FIGURE 2. Inverting Summing Amplifier 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 * Fax (510) 687-3333 http://www.calex.com 1 CALEX FaxFACTS: 321 1997 Where Fc is the -3 dB frequency in Hz of the low pass function. The roll off is 6 dB per octave or -20 dB per decade of frequency. Models 152 & 155 Operational Amplifiers AC Coupled Inverting Amplifier An AC coupled amplifier or high pass filter amplifier (Figure 3) is also easy to construct with MK 150. This amplifier is useful for audio and other applications where the DC content of the signal is not important. Basic Design Equations: GAIN ........................... G = R6 / R14 0.1 < G < 100 R6 || RLoad > 2 kohms FIGURE 3. AC Coupled Amplifier INPUT IMPEDANCE ... Zin = R14, Midband: DC Zin = Infinity BANDWIDTH .............. bw = 3 MHz/(1+G) in Hz Value For R5 ............... R5 = R6 Value For C1 ............... C1 = 1/(2 x pi x Fc x R14) in Hz, where Fc is the lower -3 dB cutoff of the amplifier. The low frequency roll off is +6 dB or +20 dB per decade of increasing frequency. Pick C2 to minimize overshoot or ringing with a small square wave input. Increasing C2 will reduce overshoot and ringing at the output. The Differentiator The differentiator (also Figure 3) is basically a high pass filter that has the useful property of producing an output voltage that is proportional to the instantaneous derivative of the input waveform. Basic Design Equations: Voltage Output ............ Vo = -R6 x C1 x dVi/dt Vo should be as low as possible for maximum dynamic range. Utility Gain Frequency Fc = 1/(2 x pi x R6 x C1) Value for R5 ................ R5 = R6 Non-inverting Amplifier Figure 4. Shows the basic non-inverting amplifier circuit. The non-inverting amplifier or voltage follower is useful where high input impedance is required and or an in phase output voltage is required. Value for R14 and C2 Select for minimum overshoot and ringing on the output with a step input. Increase R14 and or C2 to reduce overshoot. Basic Design Equations: GAIN ........................... G = 1 + R6 / (R14 + R1) 0.1 < G < 100 Either R14 or R1 can be zero ohms for convenience R6 || RLoad > 2 kohms if R1 + R14 are not used the gain is a precision +1 (voltage follower mode). INPUT IMPEDANCE ... Zin = > 10 Meg FIGURE 4. Non-inverting Amplifier Circuit A BANDWIDTH .............. bw = 3 MHz/G in Hz Value For R5 ............... R5 = R6 || (R1 + R14) 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 * Fax (510) 687-3333 http://www.calex.com 2 CALEX FaxFACTS: 321 1997 The gain can be rolled off to a minimum gain of +1 by using C2 in the circuit. Models 152 & 155 Operational Amplifiers Specifications Model Open Loop Gain Rated Output (RL = 2k) Input Offset Voltage Initial 25C Vs. Temperature Input Bias Current Initial 25C Vs. Temperature Differential Input Impedance Input Signal Range Common Mode Differential Frequency Response Small Signal Unity Gain Frequency Full Power Bandwidth Slew Rate, min. Pow er Required Voltage Current Temperature Range Operating 152 90 dB 10V 155 100 dB 10V 6 mV 20 mV/C 1 mV 3 mV/C 200 pA 10 pA/C 1012 ohm 50 nA 0.2 nA/C 4 megohm 12V 12V 10V 10V 3 MHz 5 kHz 10V/ms 3 MHz 5 kHz 10V/ms 15V 3 mA 15V 5 mA 0 - 70C 0 - 70C FIGURE 5. MK150 Mounting Kit Schematic General Notes When driving capacitive loads or shielded cables of greater than 50pF remove the jumper for R11 and insert a 470 ohm resistor. This will prevent oscillation that will appear as an unstable DC offset to most measuring equipment. The minimum value of load resistance is 2k ohms for a rated output swing of 10 Volts. The external load must be considered along with the feedback resistance for the total load. For reduced swings the output load can be increased up to a maximum of 5 mA peak. For optimum DC stability use single point "Star" grounds to Pin B. This will prevent unwanted ground loops or "unexplained" DC offsets. FIGURE 6. MK150 Mounting Kit Dimensions For Model 155-TP1, TP2, R12, R15 and Jumper for R11 are factory installed. For Model 152-TP1, TP2, R16, and Jumper for R11 are factory installed. When the MK150 is wired in a system and it appears that something is wrong, remove the MK150 and test it individually to make sure that it functions as expected. Then troubleshoot the system from the transducer to the end, a function block at a time. A If a high precision amplifier is required with a gain of 100 or more, the 176/178 Instrumentation amplifiers are a much better choice for most systems. If all else fails please feel free to call our applications engineers; we spend time trouble shooting our own systems and can sometimes spot trouble right away. We even learn new tricks from our customers! MODEL 152 2401 Stanwell Drive Concord, CA 94520-4841 (510) 687-4411 * Fax (510) 687-3333 http://www.calex.com MODEL 155 FIGURE 7. Outline Dimensions 3 CALEX FaxFACTS: 321 1997 To order the MK150 for use with the 152, specify the MK150 as MK150-152. For use with the 155, specify the MK150 as MK150-155.