Not Recommended for New Designs
The MAX495 was manufactured for Maxim by an outside wafer
foundry using a process that is no longer available. It is not
recommended for new designs. A Maxim replacement or an industry
second-source may be available. The data sheet remains available for
existing users. The other parts on the following data sheet are not
affected.
For further information, please see the QuickView data sheet for this
part or contact technical support for assistance.
_______________General Description
The dual MAX492, quad MAX494, and single MAX495
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 150µA supply current. Even
with this low current, the op amps are capable of driving
a 1kΩload, and the input referred voltage noise is only
25nV/√Hz. In addition, these op amps can drive loads in
excess of 1nF.
The precision performance of the MAX492/MAX494/
MAX495, combined with their wide input and output
dynamic range, low-voltage single-supply operation, and
very low supply current, makes them an ideal choice for
battery-operated equipment and other low-voltage appli-
cations. The MAX492/MAX494/MAX495 are available in
DIP and SO packages in the industry-standard op-amp
pin configurations. The MAX495 is also available in the
smallest 8-pin SO: the µMAX package.
________________________Applications
Portable Equipment
Battery-Powered Instruments
Data Acquisition
Signal Conditioning
Low-Voltage Applications
____________________________Features
♦Low-Voltage Single-Supply Operation (+2.7V to +6V)
♦Rail-to-Rail Input Common-Mode Voltage Range
♦Rail-to-Rail Output Swing
♦500kHz Gain-Bandwidth Product
♦Unity-Gain Stable
♦150µA Max Quiescent Current per Op Amp
♦No Phase Reversal for Overdriven Inputs
♦200µV Offset Voltage
♦High Voltage Gain (108dB)
♦High CMRR (90dB) and PSRR (110dB)
♦Drives 1kΩLoad
♦Drives Large Capacitive Loads
♦MAX495 Available in µMAX Package—8-Pin SO
______________Ordering Information
Ordering Information continued at end of data sheet.
*
Dice are specified at T A= +25°C, DC parameters only.
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
________________________________________________________________
Maxim Integrated Products
1
1
2
3
4
8
7
6
5
VCC
OUT2
IN2-
IN2+
VEE
IN1+
IN1-
OUT1
MAX492
DIP/SO
TOP VIEW
1
2
3
4
8
7
6
5
N.C.
VCC
OUT
NULL
VEE
IN1+
IN1-
NULL
MAX495
DIP/SO/µMAX
_________________Pin Configurations
MAX187
(ADC)
GND
INPUT SIGNAL CONDITIONING FOR LOW-VOLTAGE ADC
VDD
SERIAL
INTERFACE
6
8
7
3
1
4.096V
4
AIN
5
DOUT
SCLK
CS
SHDN
REF
2
ANALOG
INPUT
+5V
6
7
4
2
3
10k
10k
MAX495
__________Typical Operating Circuit
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
19-0265; Rev 2; 9/96
PART
MAX492CPA
MAX492CSA
MAX492C/D 0°C to +70°C
0°C to +70°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
MAX492EPA
MAX492ESA -40°C to +85°C
-40°C to +85°C 8 Plastic DIP
8 SO
MAX492MJA -55°C to +125°C 8 CERDIP
Pin Configurations continued at end of data sheet.
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, 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.
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-, NULL1, NULL2)..........................±10mA
Output Short-Circuit Duration ....................Indefinite short circuit
to either supply
Voltage Applied to NULL Pins....................................VCC to VEE
Continuous Power Dissipation (TA= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ....727mW
8-Pin SO (derate 5.88mW/°C above +70°C).................471mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C).........640mW
8-Pin µMAX (derate 4.1mW/°C above +70°C)..............330mW
14-Pin Plastic DIP (derate 10.00mW/°C above +70°C)...800mW
14-Pin SO (derate 8.33mW/°C above +70°C)...............667mW
14-Pin CERDIP (derate 9.09mW/°C above +70°C).......727mW
Operating Temperature Ranges
MAX49_C_ _ ........................................................0°C to +70°C
MAX49_E_ _......................................................-40°C to +85°C
MAX49_M_ _...................................................-55°C to +125°C
Junction Temperatures
MAX49_C_ _/E_ _..........................................................+150°C
MAX49_M_ _.................................................................+175°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec).............................+300°C
VCM = VEE to VCC
VCM = VOUT = VCC / 2
VCM = VEE to VCC
VCM = VEE to VCC
VCC = 2.7V,
RL= 100kΩ,
VOUT = 0.25V to 2.45V
VCC = 2.7V to 6V
(VEE - 0.25V) ≤VCM ≤(VCC + 0.25V)
RL= 100kΩ
CONDITIONS
µA
135 150
Supply Current (per amplifier)
V2.7 6.0Operating Supply Voltage Range mA30Output Short-Circuit Current
VEE + 0.04 VEE + 0.075 V
VCC - 0.075 VCC - 0.04
Output Voltage Swing
(Note 1)
nA±0.5 ±6Input Offset Current nA±25 ±60 µV±200 ±500Input Offset Voltage
Input Bias Current
90 102
dB
90 104
Large-Signal Voltage Gain
(Note 1)
dB88 110Power-Supply Rejection Ratio
MΩ2Differential Input Resistance
VVEE - 0.25 VCC + 0.25
Common-Mode Input
Voltage Range 74 90
UNITSMIN TYP MAXPARAMETER
Sourcing
Sinking
VCC = 2.7V, RL= 1kΩ,
VOUT = 0.5V to 2.2V Sourcing
Sinking 78 90
94 105
VCC = 5.0V,
RL= 100kΩ,
VOUT = 0.25V to 4.75V
Sourcing
Sinking 92 100
98 108
VCC = 5.0V, RL= 1kΩ,
VOUT = 0.5V to 4.5V Sourcing
Sinking 86 98
98 110
VOH
VOL
VOH
VOL
RL= 1kΩVEE + 0.15 VEE + 0.20
VCC - 0.20 VCC - 0.15
150 170
VCC = 2.7V
VCC = 5V
Common-Mode Rejection Ratio dB
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________ 3
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA= 0°C to +70°C, unless otherwise noted.)
190
VCM = VEE to VCC
VCM = VOUT = VCC / 2
VCM = VEE to VCC
VCM = VEE to VCC
VOH
VOH
VCC = 2.7V, RL= 1kΩ,
VOUT = 0.5V to 2.2V
VCC = 2.7V, RL= 100kΩ,
VOUT = 0.25V to 2.45V
VOL
VOL
VCC = 2.7V to 6V Sourcing
RL= 1kΩ
(VEE - 0.20) ≤VCM ≤(VCC + 0.20)
RL= 100kΩ
CONDITIONS
Sinking
Sourcing
Sinking 76
µA
175
VEE + 0.20
Supply Current (per amplifier)
V2.7 6.0Operating Supply Voltage Range
92
VCC - 0.20 VEE + 0.075
VCC = 5.0V, RL= 100kΩ,
VOUT = 0.25V to 4.75V Sourcing
Sinking 88
V
VCC - 0.075
Output Voltage Swing
(Note 1)
nA±6Input Offset Current nA±75
92
µV±650Input Offset Voltage
Input Bias Current
VCC = 5.0V, RL= 1kΩ,
VOUT = 0.5V to 4.5V
84
Sourcing
dB
88
Sinking
Large-Signal Voltage Gain
(Note 1)
dB86
82
Power-Supply Rejection Ratio
96
VVEE - 0.20 VCC + 0.20
Common-Mode Input
Voltage Range 72
UNITSMIN TYP MAXPARAMETER
µV/°C±2Input Offset Voltage Tempco
VCC = 2.7V
VCC = 5V
VCC = 0V to 3V step, VIN = VCC / 2, AV= +1
RL= 100kΩ, CL= 100pF
To 0.1%, 2V step
µs
degrees
5
RL= 100kΩ, CL= 100pF
Turn-On Time
RL= 100kΩ, CL= 100pF
µs12Time
f = 1kHz
f = 1kHz
pA/√Hz0.1
RL= 100kΩ, CL= 15pF
Input Noise-Current Density
nV/√Hz
RL= 10kΩ, CL= 15pF, VOUT = 2Vp-p, AV= +1, f = 1kHz
25Input Noise-Voltage Density
CONDITIONS
60Phase Margin
f = 1kHz dB125Amp-Amp Isolation
dB10
kHz500Gain-Bandwidth Product
Gain Margin
V/µs0.20Slew Rate
%0.003Total Harmonic Distortion
UNITSMIN TYP MAXPARAMETER
AC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, TA= +25°C, unless otherwise noted.)
Common-Mode Rejection Ratio dB
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
4 _______________________________________________________________________________________
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA= -40°C to +85°C, unless otherwise noted.)
VCM = VEE to VCC
µV/°C
VCM = VEE to VCC
VCM = VEE to VCC
VCC = 2.7V to 6V, VCM = 0V
(VEE - 0.15) ≤VCM ≤(VCC + 0.15)
CONDITIONS
±2Input Offset Voltage Tempco
nA±8Input Offset Current nA±100
µV±950Input Offset Voltage
Input Bias Current
dB84Power-Supply Rejection Ratio
VVEE - 0.15 VCC + 0.15
Common-Mode Input
Voltage Range 68
UNITSMIN TYP MAXPARAMETER
86
VCC = 2.7V, RL= 100kΩ,
VOUT = 0.25V to 2.45V 84
92
VCC = 2.7V, RL= 1kΩ,
VOUT = 0.5V to 2.2V 76
92
VCC = 5.0V, RL= 100kΩ,
VOUT = 0.25V to 4.75V 86
96
Large-Signal Voltage Gain
(Note 1)
VCC = 5.0V, RL= 1kΩ,
VOUT = 0.5V to 4.5V 80
dB
VCC - 0.075
RL= 100kΩVEE + 0.075
VCC - 0.20
Output Voltage Swing
(Note 1) RL= 1kΩVEE + 0.20
V
Operating Supply-Voltage Range 2.7 6.0 V
185
Supply Current (per amplifier) VCM = VOUT = VCC / 2 200 µA
Sourcing
Sourcing
Sourcing
Sourcing
Sinking
Sinking
Sinking
Sinking
VOH
VOH
VOL
VOL
VCC = 2.7V
VCC = 5V
dBCommon-Mode Rejection Ratio
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________ 5
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA= -55°C to +125°C, unless otherwise noted.)
225
VCM = VEE to VCC
µV/°C
VCM = VOUT = VCC / 2
VCM = VEE to VCC
VCM = VEE to VCC
VCC = 2.7V
VOH
VOH
VCC = 2.7V, RL= 1kΩ,
VOUT = 0.5V to 2.2V
VCC = 2.7V, RL= 100kΩ,
VOUT = 0.25V to 2.45V
VOL
VOL
VCC = 2.7V to 6V Sourcing
VCC = 5V
RL= 1kΩ
(VEE - 0.05V) ≤VCM ≤(VCC + 0.05V)
RL= 100kΩ
CONDITIONS
±2Input Offset Voltage Tempco
Sinking
Sourcing
Sinking 72
µA
200
VEE + 0.250
Supply Current (per amplifier)
V2.7 6.0Operating Supply-Voltage Range
90
VCC - 0.250 VEE + 0.075
VCC = 5.0V, RL= 100kΩ,
VOUT = 0.25V to 4.75V Sourcing
Sinking 82
V
VCC - 0.075
Output Voltage Swing
(Note 1)
nA±10Input Offset Current nA±200
86
mV±1.2Input Offset Voltage
Input Bias Current
VCC = 5.0V, RL= 1kΩ,
VOUT = 0.5V to 4.5V
80
Sourcing
dB
82
Sinking
Large-Signal Voltage Gain
(Note 1)
dB80
76
Power-Supply Rejection Ratio
94
VVEE - 0.05 VCC + 0.05Common-Mode Input Voltage Range 66
UNITSMIN TYP MAXPARAMETER
Note 1: RLto VEE for sourcing and VOH tests; RLto VCC for sinking and VOL tests.
dBCommon-Mode Rejection Ratio
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
6 _______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
60
-40
0.01 10 10,000
GAIN AND PHASE
vs. FREQUENCY
-20
MAX492-01
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 (DEG)
PHASE
GAIN
60
-40
0.01 10 10,000
GAIN AND PHASE
vs. FREQUENCY
-20
MAX492-02
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 (DEG)
GAIN
PHASE
140
-200.01 10 1000
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
20
MAX492-03
FREQUENCY (kHz)
PSRR (dB)
60
100
120
0
40
80
0.1 1 100
VIN = 2.5V
VEE
VCC
100
00.01 10 10,000
CHANNEL SEPARATION
vs. FREQUENCY
20
MAX492-04
FREQUENCY (kHz)
CHANNEL SEPARATION (dB)
40
60
80
120
0.1 1 100 1000
VIN = 2.5V
140
20
-30 02 6
INPUT BIAS CURRENT
vs. COMMON-MODE VOLTAGE
-20
10
MAX492-07
VCM (V)
INPUT BIAS CURRENT (nA)
4
0
-10
-25
-15
-5
5
15
1357
V
CC = 2.7V
VCC = 6V
160
0-60 -20 60 140
OFFSET VOLTAGE
vs. TEMPERATURE
40
140
MAX492-05
TEMPERATURE (°C)
OFFSET VOLTAGE (µV)
20 100
100
80
-40 0 40 80 120
20
60
120
VCM = 0V
60-60 -20 60 140
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
80
MAX492-06
TEMPERATURE (°C)
CMRR (dB)
20 100
110
100
-40 0 40 80 120
70
90
120
VCM = 0V TO +5V
VCM = -01V TO +5.1V
VCM = -0.2V TO +5.2V
VCM = -0.3V TO +5.3V
VCM = -0.4V TO +5.4V
125
-125 -60 0 100
INPUT BIAS CURRENT
vs. TEMPERATURE
-75
75
MAX492-08
TEMPERATURE (°C)
INPUT BIAS CURRENT (nA)
60
25
-25
-100
-50
0
50
100
-20 20 80 120
VCC = 2.7V
VCC = 6V
140-40 40
VCC = 6V
VCM = 0
VCM = VCC
220
0-60 -20 60 140
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
60
180
MAX492-09
TEMPERATURE (°C)
SUPPLY CURRENT PER OP AMP (µA)
20 100
140
100
200
160
120
80
40
20
-40 0 40 80 120
VOUT = VCM = VCC/2
VCC = 5V
VCC = 2.7V
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________
7
120
GAIN (dB)
110
MAX492-10
70
200
90
VCC - VOUT (mV) 500
100
80
60
50 0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1kΩ
RL = 10kΩ
RL = 100kΩ
RL = 1MΩ
VCC = +6V
RL TO VEE
120
GAIN (dB)
110
MAX492-11
70
200
90
VCC - VOUT (mV) 500
100
80
60
50 0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1kΩ
RL = 10kΩ
RL = 100kΩ
RL = 1MΩ
VCC = +2.7V
RL TO VEE
120
80 -60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX492-12
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 = 1kΩ, 0.5V < VOUT < (VCC - 0.5V)
VCC = +2.7V VCC = +6V
120
GAIN (dB)
110
MAX492-13
60
100
80
VOUT (mV) 500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50 0 200 300 400 600
RL = 1MΩ
RL = 100kΩ
RL = 10kΩ
RL = 1kΩ
VCC = +6V
RL TO VCC
100
0-60 140
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX492-16
TEMPERATURE (°C)
VOUT MIN (mV)
080
60
40
120
140
160
180
200
220
-40 -20 20 40 60 100 120
RL TO VCC
VCC = 6V, RL = 1kΩ
VCC = 2.7V, RL = 1kΩ
VCC = 6V, RL = 100kΩ
VCC = 2.7V, RL = 100kΩ
120
GAIN (dB)
110
MAX492-14
60
100
80
VOUT (mV) 500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50 0 200 300 400 600
RL = 1MΩ
RL = 100kΩ
RL = 10kΩ
RL = 1kΩ
VCC = +2.7V
RL TO VCC
120
80 -60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX492-15
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 = 100kΩ, 0.3V < VOUT < (VCC - 0.3V)
VCC = +2.7V
VCC = +6V
100
0-60 140
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX492-17
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 = 1kΩVCC = 2.7V, RL = 1kΩ
VCC = 6V, RL = 100kΩ
VCC = 2.7V, RL = 100kΩ
1000
0.01 10 10,000
OUTPUT IMPEDANCE
vs. FREQUENCY
0.1
MAX492-18
FREQUENCY (kHz)
OUTPUT IMPEDANCE (Ω)
1
10
100
0.1 1 100 1,000
VCM = VOUT = 2.5V
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
8 _______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
100
10.01 1
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
10
MAX492-19
FREQUENCY (kHz)
VOLTAGE-NOISE DENSITY (nV/√Hz)
0.1 10
INPUT REFERRED
5.0
00.01 1
CURRENT-NOISE DENSITY
vs. FREQUENCY
1.5
MAX492-20
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 + NOISE
vs. FREQUENCY
0.01
MAX492-21
FREQUENCY (Hz)
THD + NOISE (%)
100 10,000
NO LOAD
RL = 10kΩ TO GND
AV = +1
2VP-P SIGNAL
80kHz LOWPASS FILTER
VIN
50mV/div
VOUT
50mV/div
VCC = +5V, AV = +1, RL = 10kΩ
2µs/div
SMALL-SIGNAL TRANSIENT RESPONSE
0.1
0.001 4.0 4.2 4.7
TOTAL HARMONIC DISTORTION + NOISE
vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
0.01
MAX492-22
PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
THD + NOISE (%)
4.3 5.04.1 4.4 4.5 4.6 4.8 4.9
RL = 10kΩ
RL = 100kΩ
AV = +1
1kHz SINE
22kHz FILTER
RL TO GND RL = 1kΩ
RL = 2kΩ
VIN
50mV/div
VOUT
50mV/div
VCC = +5V, AV = -1, RL = 10kΩ
2µs/div
SMALL-SIGNAL TRANSIENT RESPONSE
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________ 9
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
VIN
2V/div
VOUT
2V/div
VCC = +5V, AV = -1, RL = 10kΩ
50µs/div
LARGE-SIGNAL TRANSIENT RESPONSE
VIN
2V/div
VOUT
2V/div
VCC = +5V, AV = +1, RL = 10kΩ
50µs/div
LARGE-SIGNAL TRANSIENT RESPONSE
______________________________________________________________Pin Description
Amplifier OutputOUT— Amplifier 2 Inverting InputIN2-6 Amplifier 2 OutputOUT27 Positive Power-Supply Pin. Connect to (+) terminal of power supply.VCC
8Amplifier 3 OutputOUT3—
Noninverting InputIN+— Amplifier 1 Noninverting InputIN1+3 Negative Power-Supply Pin. Connect to ground or a negative voltage.VEE
4Amplifier 2 Noninverting InputIN2+5
Amplifier 1 Inverting InputIN1-2 Inverting InputIN-—
Offset Null Input. Connect to a 10kΩpotentiometer for offset-voltage trimming.
Connect wiper to VEE (Figure 3).
NULL—
Amplifier 1 OutputOUT11
FUNCTION
MAX492 NAME
—
6
7
4
8
—
3
11
5
2
—
—
1
MAX494
6
—
—
7
—
3
—
4
—
—
2
PIN
1, 5
—
MAX495
Amplifier 3 Inverting InputIN3-— Amplifier 3 Noninverting InputIN3+— Amplifier 4 Noninverting InputIN4+—
9
10
12
—
—
—Amplifier 4 Inverting InputIN4-— Amplifier 4 OutputOUT4— No Connect. Not internally connected.N.C.—
13
14
—
—
—
8
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
10 ______________________________________________________________________________________
MAX495
10k
1
5
NULL
VEE
4NULL
Figure 2. Offset Null Circuit
__________Applications Information
The dual MAX492, quad MAX494, and single MAX495
op amps combine excellent DC accuracy with rail-to-
rail operation at both input and output. With their preci-
sion performance, wide dynamic range at low supply
voltages, and very low supply current, these op amps
are ideal for battery-operated equipment and other low-
voltage applications.
Rail-to-Rail Inputs and Outputs
The MAX492/MAX494/MAX495’s input common-mode
range extends 0.25V beyond the positive and negative
supply rails, with excellent common-mode rejection.
Beyond the specified common-mode range, the out-
puts are guaranteed not to undergo phase reversal or
latchup. Therefore, the MAX492/MAX494/MAX495 can
be used in applications with common-mode signals at
or even beyond the supplies, without the problems
associated with typical op amps.
The MAX492/MAX494/MAX495’s output voltage swings
to within 50mV of the supplies with a 100kΩload. This
rail-to-rail swing at the input and output substantially
increases the dynamic range, especially in low supply-
voltage applications. Figure 1 shows the input and out-
put waveforms for the MAX492, configured as a
unity-gain noninverting buffer operating from a single
+3V supply. The input signal is 3.0Vp-p, 1kHz sinusoid
centered at +1.5V. The output amplitude is approxi-
mately 2.95Vp-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 posi-
tive rail.
The offsets of the two pairs are trimmed; however, there
is some small 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.
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.
To adjust the MAX495’s input offset voltage (500µV max
at +25°C), connect a 10kΩtrim potentiometer between
the two NULL pins (pins 1 and 5), with the wiper con-
nected to VEE (pin 4) (Figure 2). The trim range of this
circuit is ±6mV. External offset adjustment is not avail-
able for the dual MAX492 or quad MAX494.
The input bias currents of the MAX492/MAX494/MAX495
are typically less than 50nA. 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 effec-
tive resistance seen at each input. Connect resistor R3
between the noninverting input and ground when using
VIN
VOUT
Figure 1. Rail-to-Rail Input and Output (Voltage Follower
Circuit, VCC = +3V, VEE = 0V)
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
the op amp in an inverting configuration (Figure 3a);
connect resistor R3 between the noninverting input and
the input signal when using the op amp in a noninvert-
ing configuration (Figure 3b). Select R3 to equal the
parallel combination of R1 and R2. High source resis-
tances will degrade noise performance, due to the ther-
mal noise of the resistor and the input current noise
(which is multiplied by the source resistance).
Input Stage Protection Circuitry
The MAX492/MAX494/MAX495 include internal protec-
tion 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 4). 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 (±25nA typical) is speci-
fied for the small differential input voltages. For large
differential input voltages (exceeding VF), this protec-
tion circuitry increases the input current at IN+ and IN-:
(VIN+ - VIN- ) - VF
Input Current = ———————————
2 x 1.7kΩ
For comparator applications requiring large differential
voltages (greater than VF), you can limit the input cur-
rent that flows through the diodes with external resistors
R1
VOUT
R3 = R2 II R1
R3
VIN
R2
MAX49_
Figure 3a. Reducing Offset Error Due to Bias Current:
Inverting Configuration
R3
VOUT
R3 = R2 II R1
VIN
R1
R2
MAX49_
MAX492
MAX494
MAX495
1.7kΩ
1.7kΩ
TO INTERNAL
CIRCUITRY
TO INTERNAL
CIRCUITRY
IN–
IN+
Figure 4. Input Stage Protection Circuitry
10,000
100 1 10 100
MAX492-FG 04
RESISTIVE LOAD (kΩ)
CAPACITIVE LOAD (pF)
1000
UNSTABLE REGION
VCC = +5V
VOUT = VCC/2
RL TO VEE
AV = +1
Figure 5. Capacitive-Load Stable Region Sourcing Current
______________________________________________________________________________________ 11
Figure 3b. Reducing Offset Error Due to Bias Current:
Noninverting Configuration
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
12 ______________________________________________________________________________________
in series with IN-, IN+, or both. Series resistors are not
recommended for amplifier applications, as they may
increase input offsets and decrease amplifier bandwidth.
Output Loading and Stability
Even with their low quiescent current of less than 150µA
per op amp, the MAX492/MAX494/MAX495 are well
suited for driving loads up to 1kΩwhile 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 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.
10µs/div
VIN
50mV/div
VOUT
50mV/div
10µs/div
VIN
50mV/div
VOUT
50mV/div
10µs/div
VIN
50mV/div
VOUT
50mV/div
Figure 7c. MAX492 Voltage Follower with 500pF Load—
RL=
∞
Figure 7a. MAX492 Voltage Follower with 500pF Load—
RL= 5k
Ω
Figure 7b. MAX492 Voltage Follower with 500pF Load—
RL= 20k
Ω
VIN
50mV/div
VOUT
50mV/div
10µs/div
Figure 6. MAX492 Voltage Follower with 1000pF Load
(RL=
∞
)
The MAX492/MAX494/MAX495 can drive capacitive
loads in excess of 1000pF under certain conditions
(Figure 5). When driving capacitive loads, the greatest
potential for instability occurs when the op amp is
sourcing approximately 100µA. Even in this case, sta-
bility is maintained with up to 400pF of output capaci-
tance. If the output sources either more or less current,
stability is increased. These devices perform well with a
1000pF pure capacitive load (Figure 6). Figure 7 shows
the performance with a 500pF load in parallel with vari-
ous load resistors.
To increase stability while driving large capacitive
loads, connect a pull-up resistor at the output to
decrease the current that 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 8). This resistor improves the phase margin of
the circuit by isolating the load capacitor from the op
amp’s output. Figure 9a shows the MAX492 driving
10,000pF (RL≥100kΩ), while Figure 9b adds a 47Ω
isolation resistor.
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
______________________________________________________________________________________ 13
VIN
50mV/div
VOUT
50mV/div
10µs/div
VIN
50mV/div
VOUT
50mV/div
10µs/div
MAX495
VOUT
VCC
2
3
1k
1k
+5V
7
4
6
MAX49_
VOUT
VIN CL
RS
Figure 10. Power-Up Test Configuration
Figure 9b. Driving a 10,000pF Capacitive Load with a 47
Ω
Isolation Resistor
Figure 9a. Driving a 10,000pF Capacitive Load
Figure 8. Capacitive-Load Driving Circuit
MAX492/MAX494/MAX495
Because the MAX492/MAX494/MAX495 have excellent
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 MAX492/MAX494/MAX495 have a typical supply
current of 150µA 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 MAX494 to
buffer the inputs to a multi-channel analog-to-digital con-
verter (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 MAX492/MAX494/
MAX495, it takes some time for the voltages on the sup-
ply 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 follower
held at mid-supply (Figure 10), when the supply steps
from 0V to VCC, the output settles in approximately 4µs
for VCC = +3V (Figure 11a) or 10µs for VCC = +5V
(Figure 11b).
Power Supplies and Layout
The MAX492/MAX494/MAX495 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 1µF capacitor in parallel with a
0.1µF ceramic capacitor. If operating from dual sup-
plies, 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.
Rail-to-Rail Buffers
The
Typical Operating Circuit
shows a MAX495 gain-of-
two buffer driving the analog input to a MAX187 12-bit
ADC. Both devices run from a single 5V supply, and the
converter’s internal reference is 4.096V. The MAX495’s
typical input offset voltage is 200µV. This results in an
error at the ADC input of 400µV, or less than half of one
least significant bit (LSB). Without offset trimming, the
op amp contributes negligible error to the conversion
result.
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
14 ______________________________________________________________________________________
VCC
1V/div
VOUT
500mV/div
5µs/div
VCC
2V/div
VOUT
1V/div
5µs/div
Figure 11b. Power-Up Settling Time (VCC = +5V)Figure 11a. Power-Up Settling Time (VCC = +3V)
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
______________________________________________________________________________________ 15
_Ordering Information (continued)
____Pin Configurations (continued)
_________________Chip Topographies
TRANSISTOR COUNT: 134 (single MAX495)
268 (dual MAX492)
536 (quad MAX494)
SUBSTRATE CONNECTED TO VEE
OUT2
VCC
VCC
VEE
IN1+ IN1-
IN2-
IN2+
0.068"
(1.728mm)
0.069"
(1.752mm)
OUT1
VCC
MAX492
OUT
VCC
IN-
NULL1
NULL2
0.056"
(1.422mm)
0.055"
(1.397mm)
IN+
VEE
MAX495
* Dice are specified at TA= +25°C, DC parameters only.
TOP VIEW
14
13
12
11
10
9
8
1
2
3
4
5
6
7
OUT4
IN4-
IN4+
VEE
VCC
IN1+
IN1-
OUT1
MAX494
IN3+
IN3-
OUT3
OUT2
IN2-
IN2+
DIP/SO
PART
MAX494CPD
MAX494CSD
MAX494EPD -40°C to +85°C
0°C to +70°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
14 Plastic DIP
14 SO
14 Plastic DIP
MAX494ESD
MAX494MJD -55°C to +125°C
-40°C to +85°C 14 SO
14 CERDIP
MAX495CPA
MAX495CSA
MAX495CUA 0°C to +70°C
0°C to +70°C
0°C to +70°C 8 Plastic DIP
8 SO
8 µMAX
MAX495C/D
MAX495EPA -40°C to +85°C
0°C to +70°C Dice*
8 Plastic DIP
MAX495ESA -40°C to +85°C 8 SO
MAX495MJA -55°C to +125°C 8 CERDIP
MAX492/MAX494/MAX495
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
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
________________________________________________________Package Information
L
α
C
A1B
DIM
A
A1
B
C
D
E
e
H
L
α
MIN
0.036
0.004
0.010
0.005
0.116
0.116
0.188
0.016
0°
MAX
0.044
0.008
0.014
0.007
0.120
0.120
0.198
0.026
6°
MIN
0.91
0.10
0.25
0.13
2.95
2.95
4.78
0.41
0°
MAX
1.11
0.20
0.36
0.18
3.05
3.05
5.03
0.66
6°
INCHES MILLIMETERS
8-PIN µMAX
MICROMAX SMALL-OUTLINE
PACKAGE
0.650.0256
A
e
E H
D
0.101mm
0.004 in
21-0036D
DIM
A
A1
B
C
E
e
H
L
MIN
0.053
0.004
0.014
0.007
0.150
0.228
0.016
MAX
0.069
0.010
0.019
0.010
0.157
0.244
0.050
MIN
1.35
0.10
0.35
0.19
3.80
5.80
0.40
MAX
1.75
0.25
0.49
0.25
4.00
6.20
1.27
INCHES MILLIMETERS
21-0041A
Narrow SO
SMALL-OUTLINE
PACKAGE
(0.150 in.)
DIM
D
D
D
MIN
0.189
0.337
0.386
MAX
0.197
0.344
0.394
MIN
4.80
8.55
9.80
MAX
5.00
8.75
10.00
INCHES MILLIMETERS
PINS
8
14
16
1.270.050
L
0°-8°
HE
D
e
A
A1 C
0.101mm
0.004in.
B
