MAXIM MAX4091AUA

19-2272; Rev 0; 1/02
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
Features
♦ Low-Voltage, Single-Supply Operation (2.7V to 6V)
________________________Applications
♦ 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)
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX4091AUK-T
-40°C to +125°C
5 SOT23-5
Portable Equipment
MAX4091ASA
-40°C to +125°C
8 SO
Battery-Powered Instruments
MAX4091AUA
-40°C to +125°C
8 µMAX
Data Acquisition and Control
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
Low-Voltage Signal Conditioning
Pin Configurations/Functional Diagrams
TOP VIEW
N.C. 1
8
N.C.
IN- 2
7
VCC
IN+ 3
6
OUT
VEE 4
5
N.C.
MAX4091
µMAX/SO
OUT 1
MAX4091
5
VCC
VEE 2
4
IN+ 3
IN-
SOT23
OUT1 1
8
VCC
IN1- 2
7
OUT2
IN1+ 3
6
IN2-
VEE 4
5
IN2+
MAX4092
µMAX/SO
OUT1 1
14 OUT4
IN1- 2
13 IN4-
IN1+ 3
12 IN4+
VCC 4
MAX4094
11 VEE
IN2+ 5
10 IN3+
IN2- 6
9
IN3-
OUT2 7
8
OUT3
TSSOP/SO
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX4091/MAX4092/MAX4094
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 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.
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
ABSOLUTE MAXIMUM RATINGS
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
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.
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
6.0
V
VCC = 2.7V
115
165
VCC = 5V
130
185
DC CHARACTERISTICS
Supply Voltage Range
VCC
Inferred from PSRR test
2.7
Supply Current
ICC
VCM = VCC/2
Input Offset Voltage
VOS
VCM = VEE to VCC
0.03
1.4
mV
IB
VCM = VEE to VCC
20
180
nA
Input Offset Current
IOS
VCM = VEE to VCC
7
nA
Input Common-Mode Range
VCM
Inferred from CMRR test
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
VCC = 2.7V, RL = 100kΩ Sourcing
0.25V ≤ VOUT ≤ 2.45V
Sinking
83
105
81
105
Sourcing
91
105
Input Bias Current
Large-Signal Voltage Gain
(Note 1)
AVOL
VCC = 2.7V, RL = 1kΩ
0.5V ≤ VOUT ≤ 2.2V
0.2
VEE - 0.05
Sinking
VCC = 5.0V, RL = 100kΩ Sourcing
0.25V ≤ VOUT ≤ 4.75V
Sinking
VCC = 5.0V, RL = 1kΩ
0.5V ≤ VOUT ≤ 4.5V
Output Voltage Swing High
(Note 1)
VOH
|VCC - VOUT|
Output Voltage Swing Low
(Note 1)
VOL
|VOUT - VEE|
78
90
87
115
83
115
Sourcing
97
110
Sinking
84
100
µA
dB
RL = 100kΩ
15
69
RL = 1kΩ
130
210
RL = 100kΩ
15
70
RL = 1kΩ
80
220
mV
mV
AC CHARACTERISTICS
Gain-Bandwidth Product
Phase Margin
GBWP
RL = 100kΩ, CL = 100pF
500
kHz
φM
RL = 100kΩ, CL = 100pF
60
degrees
Gain Margin
Slew Rate
2
SR
RL = 100kΩ, CL = 100pF
10
dB
RL = 100kΩ, CL = 15pF
0.20
V/µs
_______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25°C.)
PARAMETER
SYMBOL
Input-Noise Voltage Density
eN
Input-Noise Current Density
CONDITIONS
MIN
TYP
THD + N
Capacitive-Load Stability
CLOAD
Settling Time
tS
Power-On Time
tON
Op-Amp Isolation
UNITS
f = 10kHz
12
nV/√Hz
f = 10kHz
1.5
pA/√Hz
16
µVRMS
f = 1kHz, RL = 10kΩ, CL = 15pF,
AV = 1, VOUT = 2VP-P
0.003
%
AV = 1
2000
pF
To 0.1%, 2V step
12
µs
VCC = 0 to 3V step, VIN = VCC/2,
AV = 1
2
µs
125
dB
Noise Voltage
(0.1Hz to 10Hz)
Total Harmonic Distortion
Plus Noise
MAX
f = 1kHz (MAX4092/MAX4094)
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
6.0
V
DC CHARACTERISTICS
Supply Voltage Range
Supply Current
Input Offset Voltage
Input Offset Voltage Tempco
Input Bias Current
VCC
Inferred from PSRR test
ICC
VCM = VCC/2
VOS
VCM = VEE to VCC
2.7
VCC = 2.7V
200
VCC = 5V
225
±3.5
∆VOS/∆T
±2
IB
VCM = VEE to VCC
Input Offset Current
IOS
VCM = VEE to VCC
Input Common-Mode Range
VCM
Inferred from CMRR test
VEE - 0.05
µA
mV
µV/°C
±200
nA
±20
nA
VCC + 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
VCC = 2.7V, RL = 100kΩ
0.25V ≤ VOUT ≤ 2.45V
Large-Signal Voltage Gain
(Note 1)
AVOL
VCC = 2.7V, RL = 1kΩ
0.5V ≤ VOUT ≤ 2.2V
Sourcing
82
Sinking
80
Sourcing
90
Sinking
76
VCC = 5V, RL = 100kΩ
0.25V ≤ VOUT ≤ 4.75V
Sourcing
86
Sinking
82
VCC = 5V, RL = 1kΩ
0.5V ≤ VOUT ≤ 4.5V
Sourcing
94
Sinking
80
dB
Output Voltage Swing High
(Note 1)
VOH
VCC - VOUT
RL = 100kΩ
75
RL = 1kΩ
250
Output Voltage Swing Low
(Note 1)
VOL
VOUT - VEE
RL = 100kΩ
75
RL = 1kΩ
250
mV
mV
Note 1: RL is connected to VEE for AVOL sourcing and VOH tests. RL is 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.
_______________________________________________________________________________________
3
MAX4091/MAX4092/MAX4094
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.)
GAIN AND PHASE
vs. FREQUENCY
60
GAIN (dB)
40
20
0
PHASE
-60
0
GAIN
60
0
20
PHASE
140
VCC
100
-60
0
VIN = 2.5V
120
MAX4091 toc03
120
40
GAIN (dB)
GAIN
180
CL = 470pF
AV = 1000
RL = ∞
60
120
PHASE (DEGREES)
60
MAX4091 toc02
80
180
AV = 1000
NO LOAD
PSRR (dB)
MAX4091 toc01
80
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
PHASE (DEGREES)
GAIN AND PHASE
vs. FREQUENCY
80
60
VEE
40
20
0
1
10
100
-180
1000 10,000
-20
0.01
0.1
1
100
10
CHANNEL ISOLATION
vs. FREQUENCY
OFFSET VOLTAGE
vs. TEMPERATURE
OFFSET VOLTAGE vs.
COMMON-MODE VOLTAGE
VCM = 0
140
60
40
100
80
60
OFFSET VOLTAGE (µV)
80
120
100
80
60
1000
MAX4091 toc06
160
OFFSET VOLTAGE (mV)
100
40
40
VCC = 2.7V
20
0
-20
VCC = 6V
-40
-60
20
20
0
0.01
-80
0
0.1
1
10
100
1000 10,000
-100
-60 -40 -20 0
20 40 60 80 100 120 140
-1
0
1
2
3
4
TEMPERATURE (°C)
COMMON-MODE VOLTAGE (V)
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
INPUT BIAS CURRENT vs.
COMMON-MODE VOLTAGE
INPUT BIAS CURRENT vs.
TEMPERATURE
VCM = -0.2V TO +5.2V
VCM = -0.3V TO +5.3V
VCM = -0.4V TO +5.4V
50
20 40 60 80 100 120 140
TEMPERATURE (°C)
VCC = 2.7V
10
30
5
0
-5
-10
-15
3
4
5
6
125
-10
-20
-40
2
VCC = 2.7V
0
-25
COMMON-MODE VOLTAGE (V)
100
10
-30
1
VCC = 6V
VCM = VCC
20
-20
0
MAX4091 toc09
MAX4091 toc08
15
7
40
INPUT BIAS CURRENT (nA)
80
VCC = 6V
20
INPUT BIAS CURRENT (nA)
90
-60 -40 -20 0
25
MAX4091 toc07
VCM = 0 TO 5V
VCM = -0.1V TO +5.1V
6
5
FREQUENCY (kHz)
110
4
10
FREQUENCY (kHz)
120
60
1
FREQUENCY (kHz)
VIN = 2.5V
70
0.1
FREQUENCY (kHz)
140
CHANNEL SEPARATION (dB)
-40
0.01
-180
1000 10,000
100
MAX4091 toc05
0.1
MAX4901 toc04
-40
0.01
100
-120
-20
-120
-20
CMRR (dB)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
VCM = 0
VCC = 6V
-50
-25
0
25
50
75
TEMPERATURE (°C)
_______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
100
80
60
40
0
120
0
25
50
75
100
2
3
4
5
6
LARGE-SIGNAL GAIN
vs. TEMPERATURE
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
80
70
115
VCC = 2.7V
RL TO VEE
60
110
RL = 1kW, 0.5V < VOUT < (VCC - 0.5V)
RL TO VCC
100
VCC = 2.7V
95
VCC = 6V
500
RL = 1kW
RL = 10kW
60
RL TO VCC
110
VCC = 6V
105
100
95
RL TO VEE
200
300 400
VOUT (mV)
500
600
400
500
600
180
RL TO VCC
VCC = 6V, RL = 1kW
160
140
VCC = 2.7V, RL = 1kW
120
100
80
40
VCC = 6V, RL = 100kW
VCC = 2.7V, RL = 100kW
20
0
80
100
200
60
90
85
50
300
220
MAX4091 toc17
115
RL = 100kW, 0.3V < VOUT < (VCC - 0.3V)
200
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
VCC = 2.7V
VCC = 2.7V
RL TO VCC
0
100
VOUT (mV)
MINIMUM VOUT (nV)
90
120
LARGE-SIGNAL GAIN (dB)
MAX4091 toc16
RL = 1MW
100
70
VCC = 6V
RL TO VCC
0
20 40 60 80 100 120 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
120
80
RL = 1kW
RL = 10kW
80
TEMPERATURE (°C)
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 100kW
90
50
-60 -40 -20 0
600
RL = 100kW
60
80
400
200 300
VCC - VOUT (mV)
600
70
RL TO VEE
85
50
500
RL = 1MW
110
100
105
90
100
120
GAIN (dB)
RL = 100kW
RL = 10kW
RL = 1kW
90
120
0
MAX4091 toc14
MAX4091 toc13
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
GAIN (dB)
50
1
400
200 300
VCC - VOUT (mV)
110
110
VCC = 6V
RL TO VEE
60
SUPPLY VOLTAGE (V)
RL = 1MW
100
80
TEMPERATURE (°C)
120
0
RL = 1kW
70
80
125
LARGE-SIGNAL GAIN (dB)
-25
RL = 100kW
90
100
40
-50
RL = 1MW
100
140
60
20
GAIN (dB)
160
MAX4091 toc15
VCC = 2.7V
120
RL = 10kW
110
MAX4091 toc18
140
180
GAIN (dB)
VCC = 5V
160
120
MAX4091 toc11
180
200
SUPPLY CURRENT PER AMP (µA)
VOUT = VCM = VCC/2
200
SUPPLY CURRENT PER AMP (µA)
MAX4091 toc10
220
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
SUPPLY CURRENT PER AMPLIFIER
vs. SUPPLY VOLTAGE
MAX4091 toc12
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (°C)
-60 -40 -20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX4091/MAX4092/MAX4094
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA = +25°C, unless otherwise noted.)
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
OUTPUT IMPEDANCE
vs. FREQUENCY
VCC = 2.7V, RL = 1kW
120
100
80
VCC = 6V, RL = 100kW
VCC = 2.7V, RL = 100kW
40
100
10
1
20
0
100
INPUT REFERRED
1
0.1
0.01
-60 -40 -20 0 20 40 60 80 100 120 140
10
0.1
1
10
100
1,000 10,000
0.01
10
FREQUENCY (kHz)
FREQUENCY (kHz)
CURRENT-NOISE DENSITY
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
4.5
4.0
0.1
MAX4091 toc23
0.1
MAX4091 toc22
5.0
AV = 1
2VP-P SIGNAL
80kHz LOWPASS FILTER
AV = 1
1kHz SINE
22kHz FILTER
RL TO GND
THD + N (%)
3.0
2.5
2.0
0.01
THD + N (%)
3.5
RL = 10kW TO GND
RL = 1kW
RL = 2kW
0.01
1.5
RL = 100kW
RL = 10kW
1.0
INPUT REFERRED
0.5
NO LOAD
0
0.001
0.001
0.01
1
0.1
10
10
FREQUENCY (kHz)
1000
100
10,000
4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0
PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE
LARGE-SIGNAL TRANSIENT RESPONSE
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4091 toc25
MAX4091 toc27
MAX4091 toc26
VCC = 5V, AV = 1, RL = 10kΩ
VCC = 5V, AV = -1, RL = 10kΩ
VCC = 5V, AV = 1, RL = 10kΩ
VIN
50mV/div
VIN
50mV/div
VIN
2V/div
VOUT
50mV/div
VOUT
50mV/div
VOUT
2V/div
2µs/div
6
1
0.1
TEMPERATURE (°C)
MAX4091 toc24
60
VCM = VOUT = 2.5V
MAX4091 toc21
VCC = 6V, RL = 1kW
140
1000
VOLTAGE-NOISE DENSITY (nV/ÖHz)
160
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
MAX40912 toc20
RL TO VEE
MAX4091 toc19
180
OUTPUT IMPEDANCE (W)
(VCC - VOUT) (mV)
200
CURRENT-NOISE DENSITY (pA/√Hz)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
2µs/div
20µs/div
_______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
SINK CURRENT vs.
OUTPUT VOLTAGE
SOURCE CURRENT vs.
SUPPLY VOLTAGE
VDIFF = 100mV
-2
OUTPUT CURRENT (mA)
VIN
2V/div
VOUT
2V/div
-6
-8
-10
-12
-14
VCC = 2.7V
-16
VCC = 6V
VDIFF = 100mV
25
OUTPUT CURRENT (mA)
-4
30
MAX4091 toc30
0
MAX4091 toc28
VCC = 5V, AV = -1, RL = 10kΩ
MAX4091 toc29
LARGE-SIGNAL TRANSIENT RESPONSE
VCC = 6V
20
15
10
VCC = 2.7V
5
-18
-20
0
0
20µs/div
0.5
1.0
1.5
2.0
2.5
3.0
1.0
2.0
OUTPUT VOLTAGE (V)
3.0
4.0
5.0
6.0
SUPPLY VOLTAGE (V)
Pin Description
PIN
NAME
FUNCTION
MAX4091
SOT23
1
MAX4091
SO/µMAX
6
—
—
OUT
Amplifier Output
2
4
4
11
VEE
Negative Supply
3
3
—
—
IN+
Noninverting Input
4
2
—
—
IN-
Inverting Input
5
7
8
4
VCC
Positive Supply
—
1, 5, 8
—
—
N.C.
No Connection. Not internally connected.
—
—
1
1
OUT1
—
—
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
—
—
—
8
OUT3
—
—
—
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
MAX4092
MAX4094
Amplifier 1 Output
Amplifier 2 Output
Amplifier 3 Output
Amplifier 4 Output
_______________________________________________________________________________________
7
MAX4091/MAX4092/MAX4094
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
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 3.0VP-P, a 1kHz
sinusoid centered at 1.5V. The output amplitude is
approximately 2.98VP-P.
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 VF is 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-:
INPUT CURRENT =
[(VIN + ) − (VIN − )] − VF
2 ✕ 1.7kΩ
Output Loading and Stability
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.
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 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,
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 Offset Voltage
8
_______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
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 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 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
_______________________________________________________________________________________
9
MAX4091/MAX4092/MAX4094
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 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 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.
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
Test Circuits/Timing Diagrams
VCC = 3V
VEE = 0
R2
VIN
1V/div
R1
VIN
VOUT
MAX409_
VOUT
1V/div
R3
R3 = R2 II R1
200µs/div
Figure 1. Rail-to-Rail Input and Output Operation
Figure 2a. Reducing Offset Error Due to Bias Current: Inverting
Configuration
R3
1.7kΩ
VIN
IN+
TO INTERNAL
CIRCUITRY
VOUT
MAX409_
R2
R3 = R2 II R1
R1
IN–
1.7kΩ
Figure 2b. Reducing Offset Error Due to Bias Current:
Noninverting Configuration
10
TO INTERNAL
CIRCUITRY
Figure 3. Input Stage Protection Circuitry
______________________________________________________________________________________
MAX4091
MAX4092
MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
10,000
CAPACITIVE LOAD (pF)
RL = ∞
UNSTABLE REGION
VIN
50mV/div
1000
VOUT
50mV/div
VCC = 5V
VOUT = VCC/2
RL TO VEE
AV = 1
100
1
10
100
10µs/div
RESISTIVE LOAD (kΩ)
Figure 4. Capacitive-Load Stable Region Sourcing Current
Figure 5. MAX4092 Voltage Follower with 1000pF Load
RL = 5kΩ
RL = 20kΩ
VIN
50mV/div
VIN
50mV/div
VOUT
50mV/div
VOUT
50mV/div
10µs/div
Figure 6a. MAX4092 Voltage Follower with 500pF Load
(RL = 5kΩ)
10µs/div
Figure 6b. MAX4092 Voltage Follower with 500pF Load
(RL = 20kΩ)
______________________________________________________________________________________
11
MAX4091/MAX4092/MAX4094
Test Circuits/Timing Diagrams (continued)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
Test Circuits/Timing Diagrams (continued)
RL = ∞
VIN
50mV/div
RS
VOUT
MAX409_
CL
VIN
VOUT
50mV/div
10µs/div
Figure 6c. MAX4092 Voltage Follower with 500pF Load
(RL = ∞)
VIN
50mV/div
VIN
50mV/div
VOUT
50mV/div
VOUT
50mV/div
10µs/div
Figure 8a. Driving a 5000pF Capacitive Load
12
Figure 7. Capacitive-Load Driving Circuit
10µs/div
Figure 8b. Driving a 5000pF Capacitive Load with a 47Ω
Isolation Resistor
______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
5V
VCC
VIN
1V/div
2
7
1kΩ
6
MAX409_
3
VOUT
4
VOUT
500mV/div
1kΩ
5µs/div
Figure 10a. Power-Up Settling Time (VCC = +3V)
Figure 9. Power-Up Test Configuration
VIN
2V/div
VOUT
1V/div
5µs/div
Figure 10b. Power-Up Settling Time (VCC = +5V)
______________________________________________________________________________________
13
MAX4091/MAX4092/MAX4094
Test Circuits/Timing Diagrams (continued)
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
8LUMAXD.EPS
SOT5L.EPS
MAX4091/MAX4092/MAX4094
Package Information
14
______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
SOICN.EPS
______________________________________________________________________________________
15
MAX4091/MAX4092/MAX4094
Package Information (continued)
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
TSSOP,NO PADS.EPS
MAX4091/MAX4092/MAX4094
Package Information (continued)
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.
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