General Description
The single MAX4091, dual MAX4092, and quad
MAX4094 operational amplifiers combine excellent DC
accuracy with Rail-to-Rail®operation at the input and
output. Since the common-mode voltage extends from
VCC to VEE, the devices can operate from either a sin-
gle supply (2.7V to 6V) or split supplies (±1.35V to
±3V). Each op amp requires less than 130µA of supply
current. Even with this low current, the op amps are
capable of driving a 1kΩload, and the input-referred
voltage noise is only 12nV/√Hz. In addition, these op
amps can drive loads in excess of 2000pF.
The precision performance of the MAX4091/MAX4092/
MAX4094 combined with their wide input and output
dynamic range, low-voltage, single-supply operation,
and very low supply current, make them an ideal
choice for battery-operated equipment, industrial, and
data acquisition and control applications. In addition,
the MAX4091 is available in space-saving 5-pin SOT23,
8-pin µMAX, and 8-pin SO packages. The MAX4092 is
available in 8-pin µMAX and SO packages, and the
MAX4094 is available in 14-pin TSSOP and 14-pin SO
packages.
________________________Applications
Portable Equipment
Battery-Powered Instruments
Data Acquisition and Control
Low-Voltage Signal Conditioning
Features
♦Low-Voltage, Single-Supply Operation (2.7V to 6V)
♦Beyond-the-Rails™ Inputs
♦No Phase Reversal for Overdriven Inputs
♦30µV Offset Voltage
♦Rail-to-Rail Output Swing with 1kΩLoad
♦Unity-Gain Stable with 2000pF Load
♦165µA (max) Quiescent Current Per Op Amp
♦500kHz Gain-Bandwidth Product
♦High Voltage Gain (115dB)
♦High Common-Mode Rejection Ratio (90dB) and
Power-Supply Rejection Ratio (100dB)
♦Temperature Range (-40°C to +125°C)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
________________________________________________________________ Maxim Integrated Products 1
VCC
1
OUT 1
2
3
4
8
7
6
5
VCC
OUT2
IN2-
IN2+
VEE
IN1+
IN1-
OUT1
µMAX/SO
TOP VIEW
1
2
3
4
8
7
6
5
N.C.
VCC
OUT
N.C.
VEE
IN+
IN-
N.C.
µMAX/SO
5
4IN-
3
IN+
2
VEE
SOT23
14
13
12
11
10
9
8
1
2
3
4
5
6
7
OUT4
IN4-
IN4+
VEE
VCC
IN1+
IN1-
OUT1
IN3+
IN3-
OUT3
OUT2
IN2-
IN2+
TSSOP/SO
4
MAX4091
MAX4091 MAX4092
MAX4094
Pin Configurations/Functional Diagrams
19-2272; Rev 0; 1/02
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.
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX4091AUK-T -40°C to +125°C 5 SOT23-5
MAX4091ASA -40°C to +125°C 8 SO
MAX4091AUA -40°C to +125°C 8 µMAX
MAX4092ASA -40°C to +125°C 8 SO
MAX4092AUA -40°C to +125°C 8 µMAX
MAX4094AUD -40°C to +125°C 14 TSSOP
MAX4094ASD -40°C to +125°C 14 SO
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc.
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA= +25°C.)
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.
Supply Voltage (VCC to VEE)....................................................7V
Common-Mode Input Voltage..........(VCC + 0.3V) to (VEE - 0.3V)
Differential Input Voltage .........................................±(VCC - VEE)
Input Current (IN+, IN-) ....................................................±10mA
Output Short-Circuit Duration
OUT shorted to GND or VCC .................................Continuous
Continuous Power Dissipation (TA= +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)...........571mW
8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW
8-Pin µMAX (derate 4.1mW/°C above +70°C) ............330mW
14-Pin SO (derate 8.33mW/°C above +70°C).............667mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) ........727mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
Supply Voltage Range VCC Inferred from PSRR test 2.7 6.0 V
VCC = 2.7V 115 165
Supply Current ICC VCM = VCC/2 VCC = 5V 130 185 µA
Input Offset Voltage VOS VCM = VEE to VCC 0.03 1.4 mV
Input Bias Current IBVCM = VEE to VCC 20 180 nA
Input Offset Current IOS VCM = VEE to VCC 0.2 7 nA
Inp ut C om m on- M od e Rang eV
CM Inferred from CMRR test VEE - 0.05 VCC + 0.05 V
Common-Mode Rejection
Ratio CMRR (VEE - 0.05V) ≤ VCM ≤ (VCC + 0.05V) 71 90 dB
Power-Supply Rejection
Ratio PSRR 2.7V ≤ VCC ≤ 6V 86 100 dB
Sourcing 83 105
VCC = 2.7V, RL = 100kΩ
0.25V ≤ VOUT ≤ 2.45V Sinking 81 105
Sourcing 91 105
VCC = 2.7V, RL = 1kΩ
0.5V ≤ VOUT ≤ 2.2V Sinking 78 90
Sourcing 87 115
VCC = 5.0V, RL = 100kΩ
0.25V ≤ VOUT ≤ 4.75V Sinking 83 115
Sourcing 97 110
Large-Signal Voltage Gain
(Note 1) AVOL
VCC = 5.0V, RL = 1kΩ
0.5V ≤ VOUT ≤ 4.5V Sinking 84 100
dB
RL = 100kΩ15 69
Output Voltage Swing High
(Note 1) VOH |VCC - VOUT|RL = 1kΩ130 210 mV
RL = 100kΩ15 70
Output Voltage Swing Low
(Note 1) VOL |VOUT - VEE|RL = 1kΩ80 220 mV
AC CHARACTERISTICS
Gain-Bandwidth Product GBWP RL = 100kΩ, CL = 100pF 500 kHz
Phase Margin φMRL = 100kΩ, CL = 100pF 60 d eg r ees
Gain Margin RL = 100kΩ, CL = 100pF 10 dB
Slew Rate SR RL = 100kΩ, CL = 15pF 0.20 V/µs
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input-Noise Voltage Density eNf = 10kHz 12 nV/√Hz
Input-Noise Current Density f = 10kHz 1.5 pA/√Hz
Noise Voltage
(0.1Hz to 10Hz) 16 µVRMS
Total Harmonic Distortion
Plus Noise THD + N f = 1kHz, RL = 10kΩ, CL = 15pF,
AV = 1, VOUT = 2VP-P 0.003 %
Capacitive-Load Stability CLOAD AV = 1 2000 pF
Settling Time tSTo 0.1%, 2V step 12 µs
Power-On Time tON VCC = 0 to 3V step, VIN = VCC/2,
AV = 1 2µs
Op-Amp Isolation f = 1kHz (MAX4092/MAX4094) 125 dB
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA= TMIN to TMAX, unless otherwise noted. Typical values specified at
TA= +25°C.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
Supply Voltage Range VCC Inferred from PSRR test 2.7 6.0 V
VCC = 2.7V 200
Supply Current ICC VCM = VCC/2 VCC = 5V 225 µA
Input Offset Voltage VOS VCM = VEE to VCC ±3.5 mV
Input Offset Voltage Tempco ∆VOS/∆T ±2 µV/°C
Input Bias Current IBVCM = VEE to VCC ±200 nA
Input Offset Current IOS VCM = VEE to VCC ±20 nA
Input Common-Mode Range VCM Inferred from CMRR test V
E E
- 0.05 V
C C
+ 0.05 V
Common-Mode Rejection Ratio CMRR (VEE - 0.05V) ≤ VCM ≤ (VCC + 0.05V) 62 dB
Power-Supply Rejection Ratio PSRR 2.7V ≤ VCC ≤ 6V 80 dB
Sourcing 82
VCC = 2.7V, RL = 100kΩ
0.25V ≤ VOUT ≤ 2.45V Sinking 80
Sourcing 90
VCC = 2.7V, RL = 1kΩ
0.5V ≤ VOUT ≤ 2.2V Sinking 76
Sourcing 86
VCC = 5V, RL = 100kΩ
0.25V ≤ VOUT ≤ 4.75V Sinking 82
Sourcing 94
Large-Signal Voltage Gain
(Note 1) AVOL
VCC = 5V, RL = 1kΩ
0.5V ≤ VOUT ≤ 4.5V Sinking 80
dB
RL = 100kΩ75
Output Voltage Swing High
(Note 1) VOH VCC - VOUTRL = 1kΩ250 mV
RL = 100kΩ75
Output Voltage Swing Low
(Note 1) VOL VOUT - VEERL = 1kΩ250 mV
Note 1: RLis connected to VEE for AVOL sourcing and VOH tests. RLis connected to VCC for AVOL sinking and VOL tests.
Note 2: All specifications are 100% tested at TA= +25°C. Specification limits over temperature (TA= TMIN to TMAX) are guaranteed
by design, not production tested.
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
4 _______________________________________________________________________________________
60
-40
0.01 10 10,000
GAIN AND PHASE
vs. FREQUENCY
-20
MAX4091 toc01
FREQUENCY (kHz)
GAIN (dB)
0
20
40
80
0.1 1 100 1000
-180
-120
-60
0
60
120
180
AV = 1000
NO LOAD
PHASE (DEGREES)
PHASE
GAIN
60
-40
0.01 10 10,000
GAIN AND PHASE
vs. FREQUENCY
-20
MAX4091 toc02
FREQUENCY (kHz)
GAIN (dB)
0
20
40
80
0.1 1 100 1000
-180
-120
-60
0
60
120
180
CL = 470pF
AV = 1000
RL = ∞
PHASE (DEGREES)
GAIN
PHASE
140
-20
0.01 10 1000
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
20
MAX4091 toc03
FREQUENCY (kHz)
PSRR (dB)
60
100
120
0
40
80
0.1 1 100
VIN = 2.5V
VEE
VCC
100
0
0.01 10 10,000
CHANNEL ISOLATION
vs. FREQUENCY
20
MAX4901 toc04
FREQUENCY (kHz)
CHANNEL SEPARATION (dB)
40
60
80
120
0.1 1 100 1000
VIN = 2.5V
140 160
0
-60 -20 60 140
OFFSET VOLTAGE
vs. TEMPERATURE
40
140
MAX4091 toc05
TEMPERATURE (
°
C)
OFFSET VOLTAGE (
m
V)
20 100
100
80
-40 0 40 80 120
20
60
120
VCM = 0
OFFSET VOLTAGE vs.
COMMON-MODE VOLTAGE
MAX4091 toc06
COMMON-MODE VOLTAGE (V)
OFFSET VOLTAGE (µV)
653 41 20
-80
-60
-40
-20
0
20
40
60
80
100
-100
-1 7
VCC = 2.7V
VCC = 6V
50
-60 -20 60 140
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
70
MAX4091 toc07
TEMPERATURE (
°
C)
CMRR (dB)
20 100
100
90
-40 0 40 80 120
60
80
110
VCM = 0 TO 5V
VCM = -0.1V TO +5.1V
VCM = -0.2V TO +5.2V
VCM = -0.3V TO +5.3V
VCM = -0.4V TO +5.4V
INPUT BIAS CURRENT vs.
COMMON-MODE VOLTAGE
MAX4091 toc08
COMMON-MODE VOLTAGE (V)
INPUT BIAS CURRENT (nA)
54321
-20
-15
-10
-5
0
5
10
15
20
25
-25
06
VCC = 2.7V
VCC = 6V
INPUT BIAS CURRENT vs.
TEMPERATURE
MAX4091 toc09
TEMPERATURE (°C)
INPUT BIAS CURRENT (nA)
10075-25 0 25 50
-30
-20
-10
0
10
20
30
40
-40
-50 125
VCM = VCC
VCC = 2.7V
VCC = 6V
VCM = 0
VCC = 6V
Typical Operating Characteristics
(VCC = 5V, VEE = 0, TA= +25°C, unless otherwise noted.)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
MAX4091 toc10
TEMPERATURE (°C)
SUPPLY CURRENT PER AMP (µA)
1007525 500-25
20
40
60
80
100
120
140
160
180
200
220
0
-50 125
VOUT = VCM = VCC/2
VCC = 5V
VCC = 2.7V
SUPPLY CURRENT PER AMPLIFIER
vs. SUPPLY VOLTAGE
MAX4091 toc11
SUPPLY VOLTAGE (V)
SUPPLY CURRENT PER AMP (µA)
542 3
60
80
100
120
140
160
180
200
40
16
120
GAIN (dB)
110
MAX4091 toc12
70
200
90
VCC - VOUT (mV)
500
100
80
60
50
0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1k
W
RL = 10k
W
RL = 100k
W
RL = 1M
W
VCC = 6V
RL TO VEE
120
GAIN (dB)
110
MAX4091 toc13
70
200
90
VCC - VOUT (mV)
500
100
80
60
50
0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1k
W
RL = 10k
W
RL = 100k
W
RL = 1M
W
VCC = 2.7V
RL TO VEE
120
80
-60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX4091 toc14
TEMPERATURE (
°
C)
LARGE-SIGNAL GAIN (dB)
20 100
100
-40 0 40 80 120
85
95
105
115
RL TO VCC
RL TO VEE
RL = 1k
W
, 0.5V < VOUT < (VCC - 0.5V)
VCC = 2.7V
VCC = 6V
120
GAIN (dB)
110
MAX4091 toc15
60
100
80
VOUT (mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0 200 300 400 600
RL = 1M
W
RL = 100k
W
RL = 10k
W
RL = 1k
W
VCC = 6V
RL TO VCC
120
GAIN (dB)
110
MAX4091 toc16
60
100
80
VOUT (mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0 200 300 400 600
RL = 1M
W
RL = 100k
W
RL = 10k
W
RL = 1k
W
VCC = 2.7V
RL TO VCC
120
80
-60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX4091 toc17
TEMPERATURE (
°
C)
LARGE-SIGNAL GAIN (dB)
20 100
100
-40 0 40 80 120
85
95
105
115 RL TO VCC
RL TO VEE
RL = 100k
W
, 0.3V < VOUT < (VCC - 0.3V)
VCC = 2.7V
VCC = 6V
100
0
-60 140
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX4091 toc18
TEMPERATURE (
°
C)
080
60
40
120
140
160
180
200
220
-40 -20 20 40 60 100 120
RL TO VCC
VCC = 6V, RL = 1k
W
VCC = 2.7V, RL = 1k
W
VCC = 6V, RL = 100k
W
VCC = 2.7V, RL = 100k
W
MINIMUM VOUT (nV)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
6 _______________________________________________________________________________________
100
0
-60 140
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX4091 toc19
TEMPERATURE (
°
C)
(VCC - VOUT) (mV)
080
60
40
120
140
160
180
200
-40 -20 20 40 60 100 120
RL TO VEE
VCC = 6V, RL = 1k
W
VCC = 2.7V, RL = 1k
W
VCC = 6V, RL = 100k
W
VCC = 2.7V, RL = 100k
W
1000
0.01 10 10,000
OUTPUT IMPEDANCE
vs. FREQUENCY
0.1
MAX40912 toc20
FREQUENCY (kHz)
OUTPUT IMPEDANCE (
W
)
1
10
100
0.1 1 100 1,000
VCM = VOUT = 2.5V
100
1
0.01 1
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
10
MAX4091 toc21
FREQUENCY (kHz)
VOLTAGE-NOISE DENSITY (nV/
Ö
Hz)
0.1 10
INPUT REFERRED
5.0
0
0.01 1
CURRENT-NOISE DENSITY
vs. FREQUENCY
1.5
MAX4091 toc22
FREQUENCY (kHz)
CURRENT-NOISE DENSITY (pA/√Hz)
0.1 10
INPUT REFERRED
0.5
1.0
2.0
2.5
3.0
3.5
4.0
4.5
0.1
0.001
10 1000
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
0.01
MAX4091 toc23
FREQUENCY (Hz)
THD + N (%)
100 10,000
NO LOAD
RL = 10k
W
TO GND
AV = 1
2VP-P SIGNAL
80kHz LOWPASS FILTER
0.1
0.001
4.0 4.2 4.7
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
0.01
MAX4091 toc24
PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
THD + N (%)
4.3 5.04.1 4.4 4.5 4.6 4.8 4.9
RL = 10k
W
RL = 100k
W
AV = 1
1kHz SINE
22kHz FILTER
RL TO GND RL = 1k
W
RL = 2k
W
VIN
50mV/div
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4091 toc25
2µs/div
VCC = 5V, AV = 1, RL = 10kΩ
VOUT
50mV/div
VIN
50mV/div
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4091 toc26
2µs/div
VOUT
50mV/div
VCC = 5V, AV = -1, RL = 10kΩ
VIN
2V/div
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc27
20µs/div
VOUT
2V/div
VCC = 5V, AV = 1, RL = 10kΩ
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA= +25°C, unless otherwise noted.)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA= +25°C, unless otherwise noted.)
Pin Description
VIN
2V/div
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc28
20µs/div
VOUT
2V/div
VCC = 5V, AV = -1, RL = 10kΩ
SINK CURRENT vs.
OUTPUT VOLTAGE
MAX4091 toc29
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
2.52.01.51.00.5
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
-20
0 3.0
VCC = 2.7V
VCC = 6V
VDIFF = 100mV
SOURCE CURRENT vs.
SUPPLY VOLTAGE
MAX4091 toc30
SUPPLY VOLTAGE (V)
OUTPUT CURRENT (mA)
5.04.03.02.0
5
10
15
20
25
30
0
1.0 6.0
VDIFF = 100mV
VCC = 2.7V
VCC = 6V
PIN
MAX4091 MAX4091
SOT23 SO/µMAX MAX4092 MAX4094 NAME FUNCTION
16—— OUT Amplifier Output
24411 V
EE Negative Supply
33—— IN+ Noninverting Input
42—— IN- Inverting Input
5784 V
CC Positive Supply
—1, 5, 8 —— N.C. No Connection. Not internally connected.
—— 1 1 OUT1 Amplifier 1 Output
—— 2 2 IN1- Amplifier 1 Inverting Input
—— 3 3 IN1+ Amplifier 1 Noninverting Input
—— 5 5 IN2+ Amplifier 2 Noninverting Input
—— 6 6 IN2- Amplifier 2 Inverting Input
—— 7 7 OUT2 Amplifier 2 Output
——— 8 OUT3 Amplifier 3 Output
——— 9 IN3- Amplifier 3 Inverting Input
———10 IN3+ Amplifier 3 Noninverting Input
———12 IN4+ Amplifier 4 Noninverting Input
———13 IN4- Amplifier 4 Inverting Input
———14 OUT4 Amplifier 4 Output
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
8 _______________________________________________________________________________________
Detailed Description
The single MAX4091, dual MAX4092 and quad
MAX4094 op amps combine excellent DC accuracy
with rail-to-rail operation at both input and output. With
their precision performance, wide dynamic range at low
supply voltages, and very low supply current, these op
amps are ideal for battery-operated equipment, indus-
trial, and data acquisition and control applications.
Applications Information
Rail-to-Rail Inputs and Outputs
The MAX4091/MAX4092/MAX4094’s input common-
mode range extends 50mV beyond the positive and
negative supply rails, with excellent common-mode
rejection. Beyond the specified common-mode range,
the outputs are guaranteed not to undergo phase
reversal or latchup. Therefore, the MAX4091/MAX4092/
MAX4094 can be used in applications with common-
mode signals, at or even beyond the supplies, without
the problems associated with typical op amps.
The MAX4091/MAX4092/MAX4094’s output voltage
swings to within 15mV of the supplies with a 100kΩ
load. This rail-to-rail swing at the input and the output
substantially increases the dynamic range, especially
in low-supply-voltage applications. Figure 1 shows the
input and output waveforms for the MAX4092, config-
ured as a unity-gain noninverting buffer operating from
a single 3V supply. The input signal is 3.0VP-P, a 1kHz
sinusoid centered at 1.5V. The output amplitude is
approximately 2.98VP-P.
Input Offset Voltage
Rail-to-rail common-mode swing at the input is obtained
by two complementary input stages in parallel, which
feed a folded cascaded stage. The PNP stage is active
for input voltages close to the negative rail, and the NPN
stage is active for input voltages close to the positive rail.
The offsets of the two pairs are trimmed. However,
there is some residual mismatch between them. This
mismatch results in a two-level input offset characteris-
tic, with a transition region between the levels occurring
at a common-mode voltage of approximately 1.3V
above VEE. Unlike other rail-to-rail op amps, the transi-
tion region has been widened to approximately 600mV
in order to minimize the slight degradation in CMRR
caused by this mismatch.
The input bias currents of the MAX4091/MAX4092/
MAX4094 are typically less than 20nA. The bias current
flows into the device when the NPN input stage is
active, and it flows out when the PNP input stage is
active. To reduce the offset error caused by input bias
current flowing through external source resistances,
match the effective resistance seen at each input.
Connect resistor R3 between the noninverting input and
ground when using the op amp in an inverting configu-
ration (Figure 2a); connect resistor R3 between the
noninverting input and the input signal when using the
op amp in a noninverting configuration (Figure 2b).
Select R3 to equal the parallel combination of R1 and
R2. High source resistances will degrade noise perfor-
mance, due to the the input current noise (which is mul-
tiplied by the source resistance).
Input Stage Protection Circuitry
The MAX4091/MAX4092/MAX4094 include internal pro-
tection circuitry that prevents damage to the precision
input stage from large differential input voltages. This
protection circuitry consists of back-to-back diodes
between IN+ and IN- with two 1.7kΩresistors in series
(Figure 3). The diodes limit the differential voltage
applied to the amplifiers’ internal circuitry to no more
than VF, where VFis the diodes’ forward-voltage drop
(about 0.7V at +25°C).
Input bias current for the ICs (±20nA) is specified for
small differential input voltages. For large differential
input voltages (exceeding VF), this protection circuitry
increases the input current at IN+ and IN-:
Output Loading and Stability
Even with their low quiescent current of less than
130µA per op amp, the MAX4091/MAX4092/MAX4094
are well suited for driving loads up to 1kΩwhile main-
taining DC accuracy. Stability while driving heavy
capacitive loads is another key advantage over compa-
rable CMOS rail-to-rail op amps.
In op amp circuits, driving large capacitive loads
increases the likelihood of oscillation. This is especially
true for circuits with high-loop gains, such as a unity-
gain voltage follower. The output impedance and a
capacitive load form an RC network that adds a pole to
the loop response and induces phase lag. If the pole
frequency is low enough—as when driving a large
capacitive load––the circuit phase margin is degraded,
leading to either an under-damped pulse response or
oscillation.
The MAX4091/MAX4092/MAX4094 can drive capacitive
loads in excess of 2000pF under certain conditions
(Figure 4). When driving capacitive loads, the greatest
potential for instability occurs when the op amp is
sourcing approximately 200µA. Even in this case, sta-
bility is maintained with up to 400pF of output capaci-
INPUT CURRENT VVV
k
IN IN F
=−−
+−
[( ) ( )]
.217
✕Ω
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 9
tance. If the output sources either more or less current,
stability is increased. These devices perform well with a
1000pF pure capacitive load (Figure 5). Figures 6a, 6b,
and 6c show the performance with a 500pF load in par-
allel with various load resistors.
To increase stability while driving large-capacitive
loads, connect a pullup resistor to VCC at the output to
decrease the current the amplifier must source. If the
amplifier is made to sink current rather than source,
stability is further increased.
Frequency stability can be improved by adding an out-
put isolation resistor (RS) to the voltage-follower circuit
(Figure 7). This resistor improves the phase margin of
the circuit by isolating the load capacitor from the op
amp’s output. Figure 8a shows the MAX4092 driving
5000pF (RL≥100kΩ), while Figure 8b adds a 47Ωiso-
lation resistor.
Because the MAX4091/MAX4092/MAX4094 have excel-
lent stability, no isolation resistor is required, except in
the most demanding applications. This is beneficial
because an isolation resistor would degrade the low-
frequency performance of the circuit.
Power-Up Settling Time
The MAX4091/MAX4092/MAX4094 have a typical sup-
ply current of 130µA per op amp. Although supply cur-
rent is already low, it is sometimes desirable to reduce
it further by powering down the op amp and associated
ICs for periods of time. For example, when using a
MAX4092 to buffer the inputs of a multi-channel analog-
to-digital converter (ADC), much of the circuitry could
be powered down between data samples to increase
battery life. If samples are taken infrequently, the op
amps, along with the ADC, may be powered down
most of the time.
When power is reapplied to the MAX4091/MAX4092/
MAX4094, it takes some time for the voltages on the
supply pin and the output pin of the op amp to settle.
Supply settling time depends on the supply voltage, the
value of the bypass capacitor, the output impedance of
the incoming supply, and any lead resistance or induc-
tance between components. Op amp settling time
depends primarily on the output voltage and is slew-
rate limited. With the noninverting input to a voltage fol-
lower held at midsupply (Figure 9), when the supply
steps from 0 to VCC, the output settles in approximately
2µs for VCC = 3V (Figure 10a) and 8µs for VCC = 5V
(Figure 10b).
Power Supplies and Layout
The MAX4091/MAX4092/MAX4094 operate from a sin-
gle 2.7V to 6V power supply, or from dual supplies of
±1.35V to ±3V. For single-supply operation, bypass the
power supply with a 0.1µF capacitor. If operating from
dual supplies, bypass each supply to ground.
Good layout improves performance by decreasing the
amount of stray capacitance at the op amp’s inputs
and output. To decrease stray capacitance, minimize
both trace lengths and resistor leads and place exter-
nal components close to the op amp’s pins.
Chip Information
MAX4091 TRANSISTOR COUNT: 168
MAX4092 TRANSISTOR COUNT: 336
MAX4094 TRANSISTOR COUNT: 670
PROCESS: Bipolar
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
10 ______________________________________________________________________________________
Test Circuits/Timing Diagrams
VIN
1V/div
200µs/div
VOUT
1V/div
VCC = 3V
VEE = 0
Figure 1. Rail-to-Rail Input and Output Operation
R1
VOUT
R3 = R2 II R1
R3
VIN
R2
MAX409_
Figure 2a. Reducing Offset Error Due to Bias Current: Inverting
Configuration
R3
VOUT
R3 = R2 II R1
VIN
R1
R2
MAX409_
Figure 2b. Reducing Offset Error Due to Bias Current:
Noninverting Configuration
1.7kΩ
1.7kΩ
TO INTERNAL
CIRCUITRY
TO INTERNAL
CIRCUITRY
IN–
IN+
MAX4091
MAX4092
MAX4094
Figure 3. Input Stage Protection Circuitry
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 11
Test Circuits/Timing Diagrams (continued)
RESISTIVE LOAD (kΩ)
CAPACITIVE LOAD (pF)
10
1000
10,000
100
1001
UNSTABLE REGION
VCC = 5V
VOUT = VCC/2
RL TO VEE
AV = 1
Figure 4. Capacitive-Load Stable Region Sourcing Current
VIN
50mV/div
10µs/div
VOUT
50mV/div
RL = ∞
Figure 5. MAX4092 Voltage Follower with 1000pF Load
VIN
50mV/div
10µs/div
VOUT
50mV/div
RL = 5kΩ
Figure 6a. MAX4092 Voltage Follower with 500pF Load
(RL= 5kΩ)
VIN
50mV/div
10µs/div
VOUT
50mV/div
RL = 20kΩ
Figure 6b. MAX4092 Voltage Follower with 500pF Load
(RL= 20kΩ)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
12 ______________________________________________________________________________________
VIN
50mV/div
10µs/div
VOUT
50mV/div
RL = ∞
Figure 6c. MAX4092 Voltage Follower with 500pF Load
(RL= ∞)
MAX409_
VOUT
VIN
CL
RS
Figure 7. Capacitive-Load Driving Circuit
Test Circuits/Timing Diagrams (continued)
VIN
50mV/div
10µs/div
VOUT
50mV/div
Figure 8a. Driving a 5000pF Capacitive Load
VIN
50mV/div
10µs/div
VOUT
50mV/div
Figure 8b. Driving a 5000pF Capacitive Load with a 47Ω
Isolation Resistor
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 13
Test Circuits/Timing Diagrams (continued)
MAX409_
VOUT
VCC
2
3
1kΩ
1kΩ
5V
7
4
6
Figure 9. Power-Up Test Configuration
VIN
1V/div
5µs/div
VOUT
500mV/div
Figure 10a. Power-Up Settling Time (VCC = +3V)
VIN
2V/div
5µs/div
VOUT
1V/div
Figure 10b. Power-Up Settling Time (VCC = +5V)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
14 ______________________________________________________________________________________
Package Information
SOT5L.EPS
8LUMAXD.EPS
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 15
Package Information (continued)
SOICN.EPS
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
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.
16 ____________________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)
TSSOP,NO PADS.EPS
