General Description
The MAX4238/MAX4239 are low-noise, low-drift, ultra-
high precision amplifiers that offer near-zero DC offset
and drift through the use of patented autocorrelating
zeroing techniques. This method constantly measures
and compensates the input offset, eliminating drift over
time and temperature and the effect of 1/f noise. Both
devices feature Rail-to-Rail®outputs, operate from a
single 2.7V to 5.5V supply, and consume only 600µA.
An active-low shutdown mode decreases supply cur-
rent to 0.1µA.
The MAX4238 is unity-gain stable with a gain-band-
width product of 1MHz, while the decompensated
MAX4239 is stable with AV≥10V/V and a GBWP of
6.5MHz. The MAX4238/MAX4239 are available in 8-pin
narrow SO and 6-pin SOT23 packages.
Applications
Thermocouples
Strain Gauges
Electronic Scales
Medical Instrumentation
Instrumentation Amplifiers
Features
♦Ultra-Low, 0.1µV Offset Voltage
2.0µV (max) at +25°C
2.5µV (max) at -40°C to +85°C
3.5µV (max) at -40°C to +125°C
♦Low 10nV/oC Drift
♦Specified over the -40oC to +125oC Automotive
Temperature Range
♦Low Noise: 1.5µVP-P from DC to 10Hz
♦150dB AVOL, 140dB PSRR, 140dB CMRR
♦High Gain-Bandwidth Product
1MHz (MAX4238)
6.5MHz (MAX4239)
♦0.1µA Shutdown Mode
♦Rail-to-Rail Output (RL= 1kΩ)
♦Low 600µA Supply Current
♦Ground-Sensing Input
♦Single 2.7V to 5.5V Supply Voltage Range
♦Available in a Space-Saving 6-Pin SOT23 Package
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
________________________________________________________________ Maxim Integrated Products 1
MAX4238/
MAX4239
360Ω
STRAIN GUAGE
18kΩ
18kΩ
AIN
5V
AV = 100
ADC
Typical Application Circuit
19-2424; Rev 1; 12/02
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Pin Configurations appear at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Ordering Information
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX4238AUT-T -40oC to +125oC 6 SOT23-6 AAZZ
MAX4238ASA -40oC to +125oC 8 SO —
MAX4239AUT-T -40oC to +125oC 6 SOT23-6 ABAA
MAX4239ASA -40oC to +125oC 8 SO —
Selector Guide
PART MINIMUM STABLE
GAIN
GAIN
BANDWIDTH
(MHz)
MAX4238 1V/V 1
MAX4239 10V/V 6.5
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(2.7V ≤VCC ≤5.5V, VCM = GND = 0V, VOUT = VCC/2, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= +25°C,
unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Power-Supply Voltage (VCC to GND).......................................6V
All Other Pins .................................(GND - 0.3V) to (VCC + 0.3V)
Output Short-Circuit Duration
(OUT shorted to VCC or GND) ...............................Continuous
Continuous Power Dissipation (TA= +70°C)
6-Pin Plastic SOT23 (derate 9.1mW/°C above +70°C).727mW
8-Pin Plastic SO (derate 5.88mW/°C above +70°C).....471mW
Operating Temperature Range ..........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range..............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Offset Voltage VOS (Note 1) 0.1 2 µV
Long-Term Offset Drift 50 nV/1000hr
Input Bias Current IB(Note 2) 1 pA
Input Offset Current IOS (Note 2) 2 pA
Input Noise Voltage enP-P RS = 100Ω, 0.01Hz to 10Hz 1.5 µVP-P
Common-Mode Input
Voltage Range VCM Inferred from CMRR test GND
- 0.1
VCC -
1.3 V
Common-Mode Rejection Ratio CMRR -0.1V ≤ VCM ≤ VCC - 1.3V (Note 1) 120 140 dB
Power-Supply Rejection Ratio PSRR 2.7V ≤ VCC ≤ 5.5V (Note 1) 120 140 dB
0.05V ≤ V
OU T
≤ V
C C
- 0.05V
( N ote 1) RL = 10kΩ125 150
Large-Signal Voltage Gain AVOL 0.1V ≤ VOUT ≤ VCC - 0.1V
(Note 1) RL = 1kΩ125 145
dB
VCC - VOH 410
RL = 10kΩVOL 410
VCC - VOH 35 50
Output Voltage Swing VOH/VOL
RL = 1kΩVOL 35 50
mV
Output Short-Circuit Current To either supply 40 mA
Output Leakage Current 0 ≤ VOUT ≤ VCC, SHDN = GND (Note 2) 0.01 1 µA
MAX4238 0.35
Slew Rate VCC = 5V, CL = 100pF,
VOUT = 2V step MAX4239 1.6 V/µs
MAX4238 1
Gain-Bandwidth Product GBWP RL = 10kΩ, CL = 100pF,
measured at f = 100kHz MAX4239 6.5 MHz
MAX4238 1
Minimum Stable Closed-Loop
Gain
RL = 10kΩ, CL = 100pF,
phase margin = 60oMAX4239 10 V/V
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(2.7V ≤VCC ≤5.5V, VCM = GND = 0V, VOUT = VCC/2, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= +25°C,
unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4238 1000
Maximum Closed-Loop Gain RL = 10kΩ, CL = 100pF,
phase margin = 60oMAX4239 6700 V/V
0.1% (10 bit) 0.5
0.025% (12 bit) 1.0
0.006% (14 bit) 1.7
Settling Time -1V step
0.0015% (16 2.3
ms
0.1% (10 bit) 3.3
0.025% (12 bit) 4.1
0.006% (14 bit) 4.9
Overload Recovery Time AV = 10
(Note 4)
0.0015% (16 5.7
ms
0.1% (10 bit) 1.8
0.025% (12 bit) 2.6
0.006% (14 bit) 3.4
Startup Time AV = 10
0.0015% (16 4.3
ms
Supply Voltage Range VCC Inferred by PSRR test 2.7 5.5 V
SHDN = VCC, no load, VCC = 5.5V 600 850
Supply Current ICC SHDN = GND, VCC = 5.5V 0.1 1 µA
Shutdown Logic High VIH 2.2 V
Shutdown Logic Low VIL 0.8 V
Shutdown Input Current 0V ≤ V SHDN ≤ VCC 0.1 1 µA
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS
(2.7V ≤VCC ≤5.5V, VCM = GND = 0V, VOUT = VCC/2, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= -40°C to +125°C, unless other-
wise noted.) (Note 5)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
TA = -40°C to +85°C 2.5
Input Offset Voltage VOS (Note 1) TA = -40°C to +125°C 3.5 µV
Input Offset Drift TCVOS (Note 1) 10 nV/°C
Common-Mode Input Voltage
Range VCM Inferred from CMRR test GND -
0.05
VCC -
1.4 V
TA = -40°C to +85°C 115
Common-Mode Rejection Ratio CMRR
GN D - 0.05V ≤
V
C M
≤ V
C C
-
1.4V ( N ote 1) TA = -40°C to +125°C90
dB
Power-Supply Rejection Ratio PSRR 2.7V ≤ VCC ≤ 5.5V (Note 1) 120 dB
TA = -40°C to +85°C 125
RL = 10kΩ,
0.1V ≤ VOUT
≤ VCC - 0.1V
(Note 1) TA = -40°C to +125°C95
dB
0.1V ≤ VOUT ≤ VCC - 0.1V,
TA = -40°C to +85°C120
Large-Signal Voltage Gain AVOL
RL = 1kΩ
(Note 1) 0.2V ≤ VOUT ≤ VCC - 0.2V,
TA = -40°C to +125°C80
dB
VCC - VOH 20
RL = 10kΩVOL 20
VCC - VOH 100
Output Voltage Swing VOH/VOL
RL = 1kΩVOL 100
mV
Output Leakage Current 0V ≤ VOUT ≤ VCC, SHDN = GND (Note 2µA
Supply Voltage Range VCC Inferred by PSRR test 2.7 5.5 V
SHDN = VCC, no load, VCC = 5.5V 900
Supply Current ICC SHDN = GND, VCC = 5.5V 2 µA
Shutdown Logic High VIH 2.2 V
Shutdown Logic Low VIL 0.7 V
Shutdown Input Current 0V ≤ V SHDN ≤ VCC 2µA
Note 1: Guaranteed by design. Thermocouple and leakage effects preclude measurement of this parameter during production
testing. Devices are screened during production testing to eliminate defective units.
Note 2: IN+ and IN- are gates to CMOS transistors with typical input bias current of 1pA. CMOS leakage is so small that it is
impractical to test and guarantee in production. Devices are screened during production testing to eliminate defective units.
Note 3: Leakage does not include leakage through feedback resistors.
Note 4: Overload recovery time is the time required for the device to recover from saturation when the output has been
driven to either rail.
Note 5: Specifications are 100% tested at TA= +25°C, unless otherwise noted. Limits over temperature are guaranteed by design.
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
_______________________________________________________________________________________ 5
Typical Operating Characteristics
(VCC = 5V, VCM = 0V, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)
MAX4239
GAIN AND PHASE vs. FREQUENCY (TA = +25°C
)
MAX4238/39 toc09
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
MAX4238
GAIN AND PHASE vs. FREQUENCY (TA = -40°C)
MAX4238/39 toc07
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
MAX4238
GAIN AND PHASE vs. FREQUENCY (TA = +25°C
)
MAX4238/39 toc06
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
OUTPUT LOW VOLTAGE
vs. OUTPUT SINK CURRENT
MAX4238/39 toc05
SINK CURRENT (mA)
OUTPUT LOW VOLTAGE (V)
15105
0.05
0.10
0.15
0.20
0.25
0.35
0.30
0
020
VCC = 2.7V
VCC = 5V
OUTPUT HIGH VOLTAGE
vs. OUTPUT SOURCE CURRENT
MAX4238/39 toc04
SOURCE CURRENT (mA)
OUTPUT HIGH VOLTAGE (V)
15105
0.05
0.10
0.15
0.20
0.25
0.30
0
020
VOH = VCC - VOUT
VCC = 2.7V
VCC = 5V
OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE
MAX4238/39 toc03
COMMON-MODE VOLTAGE (V)
OFFSET VOLTAGE (µV)
2.71.80.9
-0.2
0
0.2
0.4
-0.4
0 3.6
TA = +125°CTA = +25°C
TA = -40°C
OFFSET VOLTAGE vs. SUPPLY VOLTAGE
MAX4238/39 toc02
SUPPLY VOLTAGE (V)
OFFSET VOLTAGE (µV)
4.84.13.4
-0.2
0
0.2
0.4
-0.4
2.7 5.5
TA = +125°C
TA = +25°CTA = -40°C
INPUT OFFSET DISTRIBUTION
MAX4238/39 toc01
OFFSET VOLTAGE (µV)
PERCENTAGE OF UNITS (%)
1.51.20.90.60.30-0.3-0.6-0.9-1.2-1.5
10
20
30
40
50
0
MAX4238
GAIN AND PHASE vs. FREQUENCY (TA = +125°C)
MAX4238/39 toc08
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
MAX4238/39 toc14
FREQUENCY (kHz)
CMRR (dB)
100100.1 1
-140
-120
-100
-80
-60
-40
-20
0
0.01 1000
-160
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX4238/39 toc13
FREQUENCY (kHz)
PSRR (dB)
100100.1 1
-140
-120
-100
-80
-60
-40
-20
0
-160
0.01 1000
MAX4239
GAIN AND PHASE vs. FREQUENCY (TA = -40°C)
MAX4238/39 toc10
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
MAX4239
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc17
AV = 10V/V
RL = 2kΩ
CL = 100pF
10µs/div
OUT
IN
500mV/div
50mV/div
MAX4238
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc15
AV = 1V/V
RL = 2kΩ
CL = 100pF
10µs/div
OUT
IN
1V/div
1V/div
MAX4239
GAIN AND PHASE vs. FREQUENCY (TA = +125°C)
MAX4238/39 toc11
FREQUENCY (Hz)
GAIN AND PHASE (dB/DEGREES)
1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
0.1k 10M
VCC = 5V
AV = 1000V/V
CL = 100pF
RL = 10kΩ
MAX4238
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4238/39 toc16
AV = 1V/V
RL = 2kΩ
CL = 100pF
10µs/div
OUT
50mV/div
IN
50mV/div
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAx4238/39 toc12
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
4321
200
300
400
500
600
0
100
05
TA = +125°C
TA = +25°C
TA = -40°C
Detailed Description
The MAX4238/MAX4239 are high-precision amplifiers
that have less than 2.5µV of input-referred offset and
low 1/f noise. These characteristics are achieved
through a patented autozeroing technique that samples
and cancels the input offset and noise of the amplifier.
The pseudorandom clock frequency varies from 10kHz
to 15kHz, reducing intermodulation distortion present in
chopper-stabilized amplifiers.
Offset Error Sources
To achieve very low offset, several sources of error
common to autozero-type amplifiers need to be consid-
ered. The first contributor is the settling of the sampling
capacitor. This type of error is independent of input-
source impedance, or the size of the external gain-set-
ting resistors. Maxim uses a patented design technique
to avoid large changes in the voltage on the sampling
capacitor to reduce settling time errors.
The second error contributor, which is present in both
autozero and chopper-type amplifiers, is the charge
injection from the switches. The charge injection
appears as current spikes at the input, and combined
with the impedance seen at the amplifier’s input, con-
tributes to input offset voltage. Minimize this
feedthrough by reducing the size of the gain-setting
resistors and the input-source impedance. A capacitor
in parallel with the feedback resistor reduces the
amount of clock feedthrough to the output by limiting
the closed-loop bandwidth of the device.
The design of the MAX4238/MAX4239 minimizes the
effects of settling and charge injection to allow specifi-
cation of an input offset voltage of 0.1µV (typ) and less
than 2.5µV over temperature (-40°C to +85°C).
1/f Noise
1/f noise, inherent in all semiconductor devices, is
inversely proportional to frequency. 1/f noise increases
3dB/octave and dominates amplifier noise at lower fre-
quencies. This noise appears as a constantly changing
voltage in series with any signal being measured. The
MAX4238/MAX4239 treat 1/f noise as a slow varying
offset error, inherently canceling the 1/f noise.
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL= 10kΩconnected to VCC/2, SHDN = VCC, TA= +25°C, unless otherwise noted.)
SHUTDOWN WAVEFORM
MAX4238/39 toc20
RL = 10kΩ
CL = 100pF
10µs/div
OUT
2V/div
1V/div
SHDN
DC TO 10Hz NOISE
MAX4238/39 toc19
VCC = 2.5V
VEE = -2.5V
1s/div
OUT 2µV/div
PIN
SOT23 SO NAME FUNCTION
1 6 OUT Amplifier Output
2 4 GND Ground
3 3 IN+ Noninverting Input
4 2 IN- Inverting Input
51SHDN
Shutdown Input. Active low
shutdown, connect to VCC for
normal operation.
67V
CC Positive Power Supply
—5, 8 N.C. No Connection. Not internally
connected.
Pin Description
MAX4238/MAX4239
Output Overload Recovery
Autozeroing amplifiers typically require a substantial
amount of time to recover from an output overload. This
is due to the time it takes for the null amplifier to correct
the main amplifier to a valid output. The MAX4238/
MAX4239 require only 3.3ms to recover from an output
overload (see Electrical Characteristics and Typical
Operating Characteristics).
Shutdown
The MAX4238/MAX4239 feature a low-power (0.1µA)
shutdown mode. When SHDN is pulled low, the clock
stops and the device output enters a high-impedance
state. Connect SHDN to VCC for normal operation.
Applications Information
Minimum and Maximum Gain
Configurations
The MAX4238 is a unity-gain stable amplifier with a gain-
bandwidth product (GBWP) of 1MHz. The MAX4239 is
decompensated for a GBWP of 6.5MHz and is stable with
a gain of 10V/V. Unlike conventional operational ampli-
fiers, the MAX4238/MAX4239 have a maximum gain
specification. To maintain stability, set the gain of the
MAX4238 between AV= 1000V/V to 1V/V, and set the
gain of the MAX4239 between AV= 6700V/V and 10V/V.
ADC Buffer Amplifier
The low offset, fast settling time, and 1/f noise cancella-
tion of the MAX4238/MAX4239 make these devices
ideal for ADC buffers. The MAX4238/MAX4239 are well
suited for low-speed, high-accuracy applications such
as strain gauges (see Typical Application Circuit).
Error Budget Example
When using the MAX4238/MAX4239 as an ADC buffer,
the temperature drift should be taken into account when
determining the maximum input signal. With a typical off-
set drift of 10nV/°C, the drift over a 10°C range is 100nV.
Setting this equal to 1/2LSB in a 16-bit system yields a
full-scale range of 13mV. With a single 2.7V supply, an
acceptable closed-loop gain is AV= 200. This provides
sufficient gain while maintaining headroom.
Chip Information
TRANSISTOR COUNT: 821
PROCESS: BiCMOS
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
8 _______________________________________________________________________________________
OUT
N.C.GND
1
2
8
7
N.C.
VCC
IN-
IN+
SHDN
SO
TOP VIEW
3
4
6
5
MAX4238/
MAX4239
MAX4238/
MAX4239
GND
IN-IN+
16V
CC
5 SHDN
OUT
SOT23
2
34
Pin Configurations
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
_______________________________________________________________________________________ 9
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
6LSOT.EPS
MAX4238/MAX4239
Ultra-Low Offset/Drift, Low-Noise,
Precision SOT23 Amplifiers
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
SOICN .EPS
PACKAGE OUTLINE, .150" SOIC
1
1
21-0041 B
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
MAX
0.010
0.069
0.019
0.157
0.010
INCHES
0.150
0.007
E
C
DIM
0.014
0.004
B
A1
MIN
0.053A
0.19
3.80 4.00
0.25
MILLIMETERS
0.10
0.35
1.35
MIN
0.49
0.25
MAX
1.75
0.050
0.016L0.40 1.27
0.3940.386D
D
MINDIM
D
INCHES
MAX
9.80 10.00
MILLIMETERS
MIN MAX
16 AC
0.337 0.344 AB8.758.55 14
0.189 0.197 AA5.004.80 8
N MS012
N
SIDE VIEW
H 0.2440.228 5.80 6.20
e 0.050 BSC 1.27 BSC
C
HE
eBA1
A
D
0-8
L
1
VARIATIONS: