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
VCCto VEE, the devices can operate from either a single 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 1kΩ load, 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 1kΩ Load
♦ 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
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
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc.
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
TOP VIEW
N.C.
IN+
V
OUT
1
MAX4091 MAX4092
IN-
2
3
4
EE
µMAX/SO
N.C.
8
V
CC
7
OUT
6
N.C.
5
V
IN+
1
MAX4091
EE
2
3
SOT23
5
4
4
OUT1
V
CC
IN-
IN1-
IN1+
V
1
2
3
4
EE
µMAX/SO
OUT1
1
IN1-
IN1+
V
IN2+
IN2-
OUT2
2
3
CC
4
MAX4094
5
6
7
TSSOP/SO
V
8
CC
OUT2
7
IN2-
6
IN2+
5
OUT4
14
IN4-
13
IN4+
12
V
11
EE
IN3+
10
IN3-
9
OUT3
8
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, V
OUT
= 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 (VCCto VEE)....................................................7V
Common-Mode Input Voltage..........(V
CC
+ 0.3V) to (VEE- 0.3V)
Differential Input Voltage .........................................±(V
CC
- VEE)
Input Current (IN+, IN-) ....................................................±10mA
Output Short-Circuit Duration
OUT shorted to GND or V
CC
.................................Continuous
Continuous Power Dissipation (T
A
= +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 V
Supply Current I
Input Offset Voltage V
Input Bias Current I
Input Offset Current I
CC
CC
OS
B
OS
Inp ut C om m on- M od e Rang eVCMInferred from CMRR test VEE - 0.05 VCC + 0.05 V
Common-Mode Rejection
Ratio
Power-Supply Rejection
Ratio
Large-Signal Voltage Gain
(Note 1)
Output Voltage Swing High
(Note 1)
Output Voltage Swing Low
(Note 1)
CMRR (V
PSRR 2.7V ≤ V
A
VOL
V
OH
V
OL
AC CHARACTERISTICS
Gain-Bandwidth Product GBWP RL = 100kΩ, CL = 100pF 500 kHz
Phase Margin φ
M
Gain Margin RL = 100kΩ, CL = 100pF 10 dB
Slew Rate SR RL = 100kΩ, CL = 15pF 0.20 V/µs
Inferred from PSRR test 2.7 6.0 V
VCM = VCC/2
VCM = VEE to V
VCM = VEE to V
VCM = VEE to V
- 0.05V) ≤ VCM ≤ (V
EE
CC
VCC = 2.7V, R
0.25V ≤ V
VCC = 2.7V, R
0.5V ≤ V
OUT
VCC = 5.0V, R
0.25V ≤ V
VCC = 5.0V, R
0.5V ≤ V
|V
|V
CC
OUT
- V
- V
OUT
OUT
VCC = 2.7V 115 165
V
CC
CC
CC
CC
≤ 6V 86 100 dB
= 100kΩ
L
≤ 2.45V
OUT
= 1kΩ
L
≤ 2.2V
= 100kΩ
L
≤ 4.75V
OUT
= 1kΩ
L
≤ 4.5V
|
|
EE
RL = 100kΩ, CL = 100pF 60 d eg r ees
= 5V 130 185
0.03 1.4 mV
20 180 nA
0.2 7 nA
+ 0.05V) 71 90 dB
CC
Sourcing 83 105
Sinking 81 105
Sourcing 91 105
Sinking 78 90
Sourcing 87 115
Sinking 83 115
Sourcing 97 110
Sinking 84 100
RL = 100kΩ 15 69
RL = 1kΩ 130 210
RL = 100kΩ 15 70
RL = 1kΩ 80 220
µA
dB
mV
mV
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, V
OUT
= VCC/2, TA= +25°C.)
ELECTRICAL CHARACTERISTICS
(VCC= 2.7V to 6V, VEE= GND, VCM= 0, V
OUT
= VCC/2, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values specified at
T
A
= +25°C.) (Note 2)
Note 1: RLis connected to VEEfor A
VOL
sourcing and VOHtests. RLis connected to VCCfor A
VOL
sinking and VOLtests.
Note 2: All specifications are 100% tested at T
A
= +25°C. Specification limits over temperature (TA= T
MIN
to T
MAX
) are guaranteed
by design, not production tested.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input-Noise Voltage Density e
N
Input-Noise Current Density f = 10kHz 1.5 pA/√Hz
Noise Voltage
(0.1Hz to 10Hz)
Total Harmonic Distortion
Plus Noise
Capacitive-Load Stability C
Settling Time t
Power-On Time t
THD + N
LOAD
S
ON
Op-Amp Isolation f = 1kHz (MAX4092/MAX4094) 125 dB
f = 10kHz 12 nV/√Hz
16 µV
f = 1kHz, RL = 10kΩ, CL = 15pF,
A
V
= 1, V
OUT
= 2V
P-P
0.003 %
AV = 1 2000 pF
To 0.1%, 2V step 12 µs
VCC = 0 to 3V step, VIN = VCC/2,
= 1
A
V
2µs
RMS
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
Supply Voltage Range V
Supply Current I
Input Offset Voltage V
CC
CC
OS
Input Offset Voltage Tempco ∆VOS/∆T ±2 µV/°C
Input Bias Current I
Input Offset Current I
Input Common-Mode Range V
B
OS
CM
Common-Mode Rejection Ratio CMRR (VEE - 0.05V) ≤ VCM ≤ (V
Power-Supply Rejection Ratio PSRR 2.7V ≤ V
Large-Signal Voltage Gain
(Note 1)
Output Voltage Swing High
(Note 1)
Output Voltage Swing Low
(Note 1)
A
V
V
VOL
OH
OL
Inferred from PSRR test 2.7 6.0 V
VCM = VCC/2
VCM = VEE to V
VCM = VEE to V
VCM = VEE to V
CC
CC
CC
Inferred from CMRR test V
≤ 6V 80 dB
CC
VCC = 2.7V, R
0.25V ≤ V
VCC = 2.7V, R
0.5V ≤ V
VCC = 5V, R
0.25V ≤ V
VCC = 5V, R
0.5V ≤ V
V
- V
CC
V
- V
OUT
OUT
OUT
OUT
EE
OUT
OUT
= 100kΩ
L
≤ 2.45V
= 1kΩ
L
≤ 2.2V
= 100kΩ
L
≤ 4.75V
= 1kΩ
L
≤ 4.5V
VCC = 2.7V 200
V
= 5V 225
CC
±3.5 mV
±200 nA
±20 nA
- 0.05 V
E E
+ 0.05V) 62 dB
CC
+ 0.05 V
C C
Sourcing 82
Sinking 80
Sourcing 90
Sinking 76
Sourcing 86
Sinking 82
Sourcing 94
Sinking 80
RL = 100kΩ 75
RL = 1kΩ 250
RL = 100kΩ 75
RL = 1kΩ 250
µA
dB
mV
mV
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
GAIN AND PHASE
80
vs. FREQUENCY
60
40
20
GAIN (dB)
0
-20
-40
0.01 10 10,000
PHASE
0.1 1 100 1000
GAIN
FREQUENCY (kHz)
MAX4091 toc01
AV = 1000
NO LOAD
180
120
60
0
PHASE (DEGREES)
-60
-120
-180
80
60
40
20
GAIN (dB)
0
-20
-40
0.01 10 10,000
CHANNEL ISOLATION
140
120
100
80
60
40
CHANNEL SEPARATION (dB)
20
0
0.01 10 10,000
vs. FREQUENCY
VIN = 2.5V
0.1 1 100 1000
FREQUENCY (kHz)
MAX4901 toc04
160
140
120
V)
m
100
80
60
OFFSET VOLTAGE (
40
20
0
-60 -20 60 140
GAIN AND PHASE
vs. FREQUENCY
CL = 470pF
A
V
R
GAIN
PHASE
0.1 1 100 1000
FREQUENCY (kHz)
L
OFFSET VOLTAGE
vs. TEMPERATURE
-40 0 40 80 120
20 100
TEMPERATURE (°C)
MAX4091 toc02
= 1000
= ∞
VCM = 0
180
120
60
0
PHASE (DEGREES)
-60
-120
-180
MAX4091 toc05
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
140
120
100
80
60
PSRR (dB)
40
20
0
-20
0.01 10 1000
V
CC
V
EE
0.1 1 100
FREQUENCY (kHz)
OFFSET VOLTAGE vs.
COMMON-MODE VOLTAGE
100
80
60
40
VCC = 2.7V
20
0
-20
OFFSET VOLTAGE (µV)
-40
-60
-80
-100
-1 7
COMMON-MODE VOLTAGE (V)
VIN = 2.5V
MAX4091 toc03
MAX4091 toc06
VCC = 6V
653 41 20
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
110
VCM = 0 TO 5V
100
V
= -0.1V TO +5.1V
CM
90
80
CMRR (dB)
70
VCM = -0.2V TO +5.2V
= -0.3V TO +5.3V
V
CM
60
V
= -0.4V TO +5.4V
CM
50
-60 -20 60 140
-40 0 40 80 120
20 100
TEMPERATURE (°C)
MAX4091 toc07
-10
INPUT BIAS CURRENT (nA)
-15
-20
-25
INPUT BIAS CURRENT vs.
COMMON-MODE VOLTAGE
25
20
15
10
5
0
-5
06
VCC = 6V
VCC = 2.7V
COMMON-MODE VOLTAGE (V)
MAX4091 toc08
54321
40
30
20
10
-10
INPUT BIAS CURRENT (nA)
-20
-30
-40
INPUT BIAS CURRENT vs.
VCM = V
CC
0
VCM = 0
-50 125
TEMPERATURE
VCC = 6V
VCC = 2.7V
VCC = 6V
TEMPERATURE (°C)
MAX4091 toc09
10075-25 0 25 50
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
V
OUT
= 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 - V
OUT
(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
R
L
TO V
EE
120
GAIN (dB)
110
MAX4091 toc13
70
200
90
VCC - V
OUT
(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
R
L
TO V
EE
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 V
CC
RL TO V
EE
RL = 1kW, 0.5V < V
OUT
< (VCC - 0.5V)
VCC = 2.7V
VCC = 6V
120
GAIN (dB)
110
MAX4091 toc15
60
100
80
V
OUT
(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
R
L
TO V
CC
120
GAIN (dB)
110
MAX4091 toc16
60
100
80
V
OUT
(mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0 200 300 400 600
RL = 1M
W
R
L
= 100k
W
RL = 10k
W
RL = 1k
W
VCC = 2.7V
R
L
TO V
CC
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 V
CC
RL TO V
EE
RL = 100kW, 0.3V < V
OUT
< (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 V
CC
VCC = 6V, RL = 1k
W
VCC = 2.7V, RL = 1k
W
VCC = 6V, RL = 100k
W
VCC = 2.7V, RL = 100k
W
MINIMUM V
OUT
(nV)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
200
RL TO V
180
160
140
120
) (mV)
OUT
100
- V
80
CC
(V
60
40
20
0
-60 140
EE
VCC = 6V, RL = 1k
VCC = 2.7V, RL = 100k
-40 -20 20 40 60 100 120
W
VCC = 2.7V, RL = 1k
VCC = 6V, RL = 100k
W
080
TEMPERATURE (°C)
1000
MAX4091 toc19
)
W
100
W
10
W
OUTPUT IMPEDANCE (
1
0.1
0.01 10 10,000
OUTPUT IMPEDANCE
vs. FREQUENCY
VCM = V
= 2.5V
OUT
0.1 1 100 1,000
FREQUENCY (kHz)
100
Hz)
Ö
MAX40912 toc20
10
VOLTAGE-NOISE DENSITY (nV/
INPUT REFERRED
1
0.01 1
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
0.1 10
FREQUENCY (kHz)
MAX4091 toc21
CURRENT-NOISE DENSITY
vs. FREQUENCY
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
INPUT REFERRED
CURRENT-NOISE DENSITY (pA/√Hz)
0.5
0
0.01 1
0.1 10
FREQUENCY (kHz)
SMALL-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = 1, RL = 10kΩ
V
IN
50mV/div
V
OUT
50mV/div
MAX4091 toc22
MAX4091 toc25
TOTAL HARMONIC DISTORTION PLUS
0.1
0.01
THD + N (%)
0.001
NOISE vs. FREQUENCY
AV = 1
SIGNAL
2V
P-P
80kHz LOWPASS FILTER
RL = 10kW TO GND
10 1000
100 10,000
FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = -1, RL = 10kΩ
V
IN
50mV/div
V
OUT
50mV/div
NO LOAD
MAX4091 toc26
MAX4091 toc23
THD + N (%)
0.001
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
0.1
AV = 1
1kHz SINE
22kHz FILTER
TO GND
R
L
0.01
4.0 4.2 4.7
PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
RL = 1k
W
RL = 2k
W
RL = 100k
RL = 10k
4.3 5.04.1 4.4 4.5 4.6 4.8 4.9
LARGE-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = 1, RL = 10kΩ
V
IN
2V/div
V
OUT
2V/div
MAX4091 toc24
W
W
MAX4091 toc27
2µs/div
2µs/div
20µs/div
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
V
IN
2V/div
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc28
20µs/div
V
OUT
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
V
DIFF
= 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
V
DIFF
= 100mV
VCC = 2.7V
VCC = 6V
MAX4091 MAX4091
SOT23 SO/µMAX
16—— OUT Amplifier Output
24411 VEENegative Supply
33—— IN+ Noninverting Input
42—— IN- Inverting Input
5784 VCCPositive 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
PIN
MAX4092 MAX4094
NAME FUNCTION
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, industrial, and data acquisition and control applications.
Applications Information
Rail-to-Rail Inputs and Outputs
The MAX4091/MAX4092/MAX4094’s input commonmode 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 commonmode 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, configured as a unity-gain noninverting buffer operating from
a single 3V supply. The input signal is 3.0V
P-P
, a 1kHz
sinusoid centered at 1.5V. The output amplitude is
approximately 2.98V
P-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 characteristic, 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 transition 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 configuration (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 performance, due to the the input current noise (which is multiplied by the source resistance).
Input Stage Protection Circuitry
The MAX4091/MAX4092/MAX4094 include internal protection 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 1.7kΩ resistors 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 1kΩ while maintaining DC accuracy. Stability while driving heavy
capacitive loads is another key advantage over comparable 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 unitygain 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, stability is maintained with up to 400pF of output capaci-
INPUT CURRENT
VVV
[( ) ( )]
=
−−
IN IN F
+−
k
.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 parallel with various load resistors.
To increase stability while driving large-capacitive
loads, connect a pullup resistor to VCCat 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 output 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 47Ω isolation resistor.
Because the MAX4091/MAX4092/MAX4094 have excellent stability, no isolation resistor is required, except in
the most demanding applications. This is beneficial
because an isolation resistor would degrade the lowfrequency performance of the circuit.
Power-Up Settling Time
The MAX4091/MAX4092/MAX4094 have a typical supply current of 130µA per op amp. Although supply current 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 analogto-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 inductance between components. Op amp settling time
depends primarily on the output voltage and is slewrate limited. With the noninverting input to a voltage follower held at midsupply (Figure 9), when the supply
steps from 0 to V
CC
, 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 single 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 external 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
Figure 1. Rail-to-Rail Input and Output Operation
Figure 2a. Reducing Offset Error Due to Bias Current: Inverting
Configuration
Figure 2b. Reducing Offset Error Due to Bias Current:
Noninverting Configuration
Figure 3. Input Stage Protection Circuitry
V
= 3V
V
1V/div
V
OUT
1V/div
CC
= 0
V
EE
IN
200µs/div
R1
V
IN
R3
R2
MAX409_
R3 = R2 II R1
V
OUT
R3
V
IN
V
MAX409_
R3 = R2 II R1
OUT
R2
R1
IN+
IN–
1.7kΩ
1.7kΩ
TO INTERNAL
CIRCUITRY
TO INTERNAL
CIRCUITRY
MAX4091
MAX4092
MAX4094
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 11
Test Circuits/Timing Diagrams (continued)
Figure 4. Capacitive-Load Stable Region Sourcing Current
Figure 5. MAX4092 Voltage Follower with 1000pF Load
Figure 6a. MAX4092 Voltage Follower with 500pF Load
(R
L
= 5kΩ)
Figure 6b. MAX4092 Voltage Follower with 500pF Load
(R
L
= 20kΩ)
10,000
UNSTABLE REGION
1000
CAPACITIVE LOAD (pF)
100
RESISTIVE LOAD (kΩ)
VCC = 5V
= VCC/2
V
OUT
TO V
R
L
EE
AV = 1
10
1001
RL = ∞
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
RL = 5kΩ
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
RL = 20kΩ
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
12 ______________________________________________________________________________________
Figure 6c. MAX4092 Voltage Follower with 500pF Load
(R
L
= ∞)
Figure 7. Capacitive-Load Driving Circuit
Test Circuits/Timing Diagrams (continued)
Figure 8a. Driving a 5000pF Capacitive Load
Figure 8b. Driving a 5000pF Capacitive Load with a 47Ω
Isolation Resistor
RL = ∞
V
IN
50mV/div
R
V
OUT
50mV/div
10µs/div
S
MAX409_
V
IN
V
OUT
C
L
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
50mV/div
V
OUT
50mV/div
V
IN
10µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 13
Test Circuits/Timing Diagrams (continued)
Figure 9. Power-Up Test Configuration
Figure 10a. Power-Up Settling Time (VCC= +3V)
Figure 10b. Power-Up Settling Time (VCC= +5V)
5V
1kΩ
1kΩ
2
3
MAX409_
V
CC
7
6
V
OUT
4
1V/div
V
OUT
500mV/div
V
IN
5µs/div
V
IN
2V/div
V
OUT
1V/div
5µs/div
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
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