_______________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 V
CC
to V
EE
,
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 150A supply current. Even
with this low current, the op amps are capable of driving
a 1k
load, 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 MAX package.
________________________Applications
Portable Equipment
Battery-Powered Instruments
Data Acquisition
Signal Conditioning
Low-Voltage Applications
____________________________Features
o
Low-Voltage Single-Supply Operation (+2.7V to +6V)
o
Rail-to-Rail Input Common-Mode Voltage Range
o
Rail-to-Rail Output Swing
o
500kHz Gain-Bandwidth Product
o
Unity-Gain Stable
o
150A Max Quiescent Current per Op Amp
o
No Phase Reversal for Overdriven Inputs
o
200V Offset Voltage
o
High Voltage Gain (108dB)
o
High CMRR (90dB) and PSRR (110dB)
o
Drives 1k
Load
o
Drives Large Capacitive Loads
o
MAX495 Available in MAX Package--8-Pin SO
______________Ordering Information
Ordering Information continued at end of data sheet.
*
Dice are specified at T
A
= +25C, 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
V
CC
OUT2
IN2-
IN2+
V
EE
IN1+
IN1-
OUT1
MAX492
DIP/SO
TOP VIEW
1
2
3
4
8
7
6
5
N.C.
V
CC
OUT
NULL
V
EE
IN1+
IN1-
NULL
MAX495
DIP/SO/
MAX
_________________Pin Configurations
MAX187
(ADC)
GND
INPUT SIGNAL CONDITIONING FOR LOW-VOLTAGE ADC
V
DD
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
MAX492
CPA
MAX492CSA
MAX492C/D
0C to +70C
0C to +70C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
MAX492EPA
MAX492ESA
-40C to +85C
-40C to +85C
8 Plastic DIP
8 SO
MAX492MJA
-55C to +125C
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
(V
CC
= 2.7V to 6V, V
EE
= GND, V
CM
= 0V, V
OUT
= V
CC
/ 2, T
A
= +25C, 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 (V
CC
to V
EE
) ....................................................7V
Common-Mode Input Voltage..........(V
CC
+ 0.3V) to (V
EE
- 0.3V)
Differential Input Voltage .........................................(V
CC
- V
EE
)
Input Current (IN+, IN-, NULL1, NULL2) ..........................10mA
Output Short-Circuit Duration ....................Indefinite short circuit
to either supply
Voltage Applied to NULL Pins ....................................V
CC
to V
EE
Continuous Power Dissipation (T
A
= +70C)
8-Pin Plastic DIP (derate 9.09mW/C above +70C) ....727mW
8-Pin SO (derate 5.88mW/C above +70C).................471mW
8-Pin CERDIP (derate 8.00mW/C above +70C).........640mW
8-Pin MAX (derate 4.1mW/C above +70C) ..............330mW
14-Pin Plastic DIP (derate 10.00mW/C above +70C)...800mW
14-Pin SO (derate 8.33mW/C above +70C)...............667mW
14-Pin CERDIP (derate 9.09mW/C above +70C).......727mW
Operating Temperature Ranges
MAX49_C_ _ ........................................................0C to +70C
MAX49_E_ _......................................................-40C to +85C
MAX49_M_ _ ...................................................-55C to +125C
Junction Temperatures
MAX49_C_ _/E_ _..........................................................+150C
MAX49_M_ _ .................................................................+175C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10sec) .............................+300C
V
CM
= V
EE
to V
CC
V
CM
= V
OUT
= V
CC
/ 2
V
CM
= V
EE
to V
CC
V
CM
= V
EE
to V
CC
V
CC
= 2.7V,
R
L
= 100k
,
V
OUT
= 0.25V to 2.45V
V
CC
= 2.7V to 6V
(V
EE
- 0.25V)
V
CM
(V
CC
+ 0.25V)
R
L
= 100k
CONDITIONS
A
135
150
Supply Current (per amplifier)
V
2.7
6.0
Operating Supply Voltage Range
mA
30
Output Short-Circuit Current
V
EE
+ 0.04 V
EE
+ 0.075
V
V
CC
- 0.075 V
CC
- 0.04
Output Voltage Swing
(Note 1)
nA
0.5
6
Input Offset Current
nA
25
60
V
200
500
Input Offset Voltage
Input Bias Current
90
102
dB
90
104
Large-Signal Voltage Gain
(Note 1)
dB
88
110
Power-Supply Rejection Ratio
M
2
Differential Input Resistance
V
V
EE
- 0.25
V
CC
+ 0.25
Common-Mode Input
Voltage Range
74
90
UNITS
MIN
TYP
MAX
PARAMETER
Sourcing
Sinking
V
CC
= 2.7V, R
L
= 1k
,
V
OUT
= 0.5V to 2.2V
Sourcing
Sinking
78
90
94
105
V
CC
= 5.0V,
R
L
= 100k
,
V
OUT
= 0.25V to 4.75V
Sourcing
Sinking
92
100
98
108
V
CC
= 5.0V, R
L
= 1k
,
V
OUT
= 0.5V to 4.5V
Sourcing
Sinking
86
98
98
110
V
OH
V
OL
V
OH
V
OL
R
L
= 1k
V
EE
+ 0.15 V
EE
+ 0.20
V
CC
- 0.20
V
CC
- 0.15
150
170
V
CC
= 2.7V
V
CC
= 5V
Common-Mode Rejection Ratio
dB
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________
3
DC ELECTRICAL CHARACTERISTICS
(V
CC
= 2.7V to 6V, V
EE
= GND, V
CM
= 0V, V
OUT
= V
CC
/ 2, T
A
= 0C to +70C, unless otherwise noted.)
190
V
CM
= V
EE
to V
CC
V
CM
= V
OUT
= V
CC
/ 2
V
CM
= V
EE
to V
CC
V
CM
= V
EE
to V
CC
V
OH
V
OH
V
CC
= 2.7V, R
L
= 1k
,
V
OUT
= 0.5V to 2.2V
V
CC
= 2.7V, R
L
= 100k
,
V
OUT
= 0.25V to 2.45V
V
OL
V
OL
V
CC
= 2.7V to 6V
Sourcing
R
L
= 1k
(V
EE
- 0.20)
V
CM
(V
CC
+ 0.20)
R
L
= 100k
CONDITIONS
Sinking
Sourcing
Sinking
76
A
175
V
EE
+ 0.20
Supply Current (per amplifier)
V
2.7
6.0
Operating Supply Voltage Range
92
V
CC
- 0.20
V
EE
+ 0.075
V
CC
= 5.0V, R
L
= 100k
,
V
OUT
= 0.25V to 4.75V
Sourcing
Sinking
88
V
V
CC
- 0.075
Output Voltage Swing
(Note 1)
nA
6
Input Offset Current
nA
75
92
V
650
Input Offset Voltage
Input Bias Current
V
CC
= 5.0V, R
L
= 1k
,
V
OUT
= 0.5V to 4.5V
84
Sourcing
dB
88
Sinking
Large-Signal Voltage Gain
(Note 1)
dB
86
82
Power-Supply Rejection Ratio
96
V
V
EE
- 0.20
V
CC
+ 0.20
Common-Mode Input
Voltage Range
72
UNITS
MIN
TYP
MAX
PARAMETER
V/C
2
Input Offset Voltage Tempco
V
CC
= 2.7V
V
CC
= 5V
V
CC
= 0V to 3V step, V
IN
= V
CC
/ 2, A
V
= +1
R
L
= 100k
, C
L
= 100pF
To 0.1%, 2V step
s
degrees
5
R
L
= 100k
, C
L
= 100pF
Turn-On Time
R
L
= 100k
, C
L
= 100pF
s
12
Time
f = 1kHz
f = 1kHz
pA/
Hz
0.1
R
L
= 100k
, C
L
= 15pF
Input Noise-Current Density
nV/
Hz
R
L
= 10k
, C
L
= 15pF, V
OUT
= 2V
p-p
, A
V
= +1, f = 1kHz
25
Input Noise-Voltage Density
CONDITIONS
60
Phase Margin
f = 1kHz
dB
125
Amp-Amp Isolation
dB
10
kHz
500
Gain-Bandwidth Product
Gain Margin
V/s
0.20
Slew Rate
%
0.003
Total Harmonic Distortion
UNITS
MIN
TYP
MAX
PARAMETER
AC ELECTRICAL CHARACTERISTICS
(V
CC
= 2.7V to 6V, V
EE
= GND, T
A
= +25C, 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
(V
CC
= 2.7V to 6V, V
EE
= GND, V
CM
= 0V, V
OUT
= V
CC
/ 2, T
A
= -40C to +85C, unless otherwise noted.)
V
CM
= V
EE
to V
CC
V/C
V
CM
= V
EE
to V
CC
V
CM
= V
EE
to V
CC
V
CC
= 2.7V to 6V, V
CM
= 0V
(V
EE
- 0.15)
V
CM
(V
CC
+ 0.15)
CONDITIONS
2
Input Offset Voltage Tempco
nA
8
Input Offset Current
nA
100
V
950
Input Offset Voltage
Input Bias Current
dB
84
Power-Supply Rejection Ratio
V
V
EE
- 0.15
V
CC
+ 0.15
Common-Mode Input
Voltage Range
68
UNITS
MIN
TYP
MAX
PARAMETER
86
V
CC
= 2.7V, R
L
= 100k
,
V
OUT
= 0.25V to 2.45V
84
92
V
CC
= 2.7V, R
L
= 1k
,
V
OUT
= 0.5V to 2.2V
76
92
V
CC
= 5.0V, R
L
= 100k
,
V
OUT
= 0.25V to 4.75V
86
96
Large-Signal Voltage Gain
(Note 1)
V
CC
= 5.0V, R
L
= 1k
,
V
OUT
= 0.5V to 4.5V
80
dB
V
CC
- 0.075
R
L
= 100k
V
EE
+ 0.075
V
CC
- 0.20
Output Voltage Swing
(Note 1)
R
L
= 1k
V
EE
+ 0.20
V
Operating Supply-Voltage Range
2.7
6.0
V
185
Supply Current (per amplifier)
V
CM
= V
OUT
= V
CC
/ 2
200
A
Sourcing
Sourcing
Sourcing
Sourcing
Sinking
Sinking
Sinking
Sinking
V
OH
V
OH
V
OL
V
OL
V
CC
= 2.7V
V
CC
= 5V
dB
Common-Mode Rejection Ratio
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________
5
DC ELECTRICAL CHARACTERISTICS
(V
CC
= 2.7V to 6V, V
EE
= GND, V
CM
= 0V, V
OUT
= V
CC
/ 2, T
A
= -55C to +125C, unless otherwise noted.)
225
V
CM
= V
EE
to V
CC
V/C
V
CM
= V
OUT
= V
CC
/ 2
V
CM
= V
EE
to V
CC
V
CM
= V
EE
to V
CC
V
CC
= 2.7V
V
OH
V
OH
V
CC
= 2.7V, R
L
= 1k
,
V
OUT
= 0.5V to 2.2V
V
CC
= 2.7V, R
L
= 100k
,
V
OUT
= 0.25V to 2.45V
V
OL
V
OL
V
CC
= 2.7V to 6V
Sourcing
V
CC
= 5V
R
L
= 1k
(V
EE
- 0.05V)
V
CM
(V
CC
+ 0.05V)
R
L
= 100k
CONDITIONS
2
Input Offset Voltage Tempco
Sinking
Sourcing
Sinking
72
A
200
V
EE
+ 0.250
Supply Current (per amplifier)
V
2.7
6.0
Operating Supply-Voltage Range
90
V
CC
- 0.250
V
EE
+ 0.075
V
CC
= 5.0V, R
L
= 100k
,
V
OUT
= 0.25V to 4.75V
Sourcing
Sinking
82
V
V
CC
- 0.075
Output Voltage Swing
(Note 1)
nA
10
Input Offset Current
nA
200
86
mV
1.2
Input Offset Voltage
Input Bias Current
V
CC
= 5.0V, R
L
= 1k
,
V
OUT
= 0.5V to 4.5V
80
Sourcing
dB
82
Sinking
Large-Signal Voltage Gain
(Note 1)
dB
80
76
Power-Supply Rejection Ratio
94
V
V
EE
- 0.05
V
CC
+ 0.05
Common-Mode Input Voltage Range
66
UNITS
MIN
TYP
MAX
PARAMETER
Note 1:
R
L
to V
EE
for sourcing and V
OH
tests; R
L
to V
CC
for sinking and V
OL
tests.
dB
Common-Mode Rejection Ratio
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
6
_______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(T
A
= +25C, V
CC
= 5V, V
EE
= 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
A
V
= +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
C
L
= 470pF
A
V
= +1000
R
L
=
PHASE (DEG)
GAIN
PHASE
140
-20
0.01
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
V
IN
= 2.5V
V
EE
V
CC
100
0
0.01
10
10,000
CHANNEL SEPARATION
vs. FREQUENCY
20
MAX492-04
FREQUENCY (kHz)
CHANNEL SEPARATION (dB)
40
60
80
120
0.1
1
100
1000
V
IN
= 2.5V
140
20
-30
0
2
6
INPUT BIAS CURRENT
vs. COMMON-MODE VOLTAGE
-20
10
MAX492-07
V
CM
(V)
INPUT BIAS CURRENT (nA)
4
0
-10
-25
-15
-5
5
15
1
3
5
7
V
CC
= 2.7V
V
CC
= 6V
160
0
-60
-20
60
140
OFFSET VOLTAGE
vs. TEMPERATURE
40
140
MAX492-05
TEMPERATURE (
C)
OFFSET VOLTAGE (
V)
20
100
100
80
-40
0
40
80
120
20
60
120
V
CM
= 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
V
CM
= 0V TO +5V
V
CM
= -01V TO +5.1V
V
CM
= -0.2V TO +5.2V
V
CM
= -0.3V TO +5.3V
V
CM
= -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
V
CC
= 2.7V
V
CC
= 6V
140
-40
40
V
CC
= 6V
V
CM
= 0
V
CM
= V
CC
220
0
-60
-20
60
140
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
60
180
MAX492-09
TEMPERATURE (
C)
SUPPLY CURRENT PER OP AMP (
A)
20
100
140
100
200
160
120
80
40
20
-40
0
40
80
120
V
OUT
= V
CM
= V
CC
/2
V
CC
= 5V
V
CC
= 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
V
CC
- V
OUT
(mV)
500
100
80
60
50
0
100
300
400
600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
R
L
= 1k
R
L
= 10k
R
L
= 100k
R
L
= 1M
V
CC
= +6V
R
L
TO V
EE
120
GAIN (dB)
110
MAX492-11
70
200
90
V
CC
- V
OUT
(mV)
500
100
80
60
50
0
100
300
400
600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
R
L
= 1k
R
L
= 10k
R
L
= 100k
R
L
= 1M
V
CC
= +2.7V
R
L
TO V
EE
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
R
L
TO V
CC
R
L
TO V
EE
R
L
= 1k
, 0.5V < V
OUT
< (V
CC
- 0.5V)
V
CC
= +2.7V
V
CC
= +6V
120
GAIN (dB)
110
MAX492-13
60
100
80
V
OUT
(mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0
200
300
400
600
R
L
= 1M
R
L
= 100k
R
L
= 10k
R
L
= 1k
V
CC
= +6V
R
L
TO V
CC
100
0
-60
140
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX492-16
TEMPERATURE (
C)
V
OUT
MIN (mV)
0
80
60
40
120
140
160
180
200
220
-40 -20
20 40 60
100 120
R
L
TO V
CC
V
CC
= 6V, R
L
= 1k
V
CC
= 2.7V, R
L
= 1k
V
CC
= 6V, R
L
= 100k
V
CC
= 2.7V, R
L
= 100k
120
GAIN (dB)
110
MAX492-14
60
100
80
V
OUT
(mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0
200
300
400
600
R
L
= 1M
R
L
= 100k
R
L
= 10k
R
L
= 1k
V
CC
= +2.7V
R
L
TO V
CC
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
R
L
TO V
CC
R
L
TO V
EE
R
L
= 100k
, 0.3V < V
OUT
< (V
CC
- 0.3V)
V
CC
= +2.7V
V
CC
= +6V
100
0
-60
140
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX492-17
TEMPERATURE (
C)
(V
CC
- V
OUT
) (mV)
0
80
60
40
120
140
160
180
200
-40 -20
20 40 60
100 120
R
L
TO V
EE
V
CC
= 6V, R
L
= 1k
V
CC
= 2.7V, R
L
= 1k
V
CC
= 6V, R
L
= 100k
V
CC
= 2.7V, R
L
= 100k
1000
0.01
10
10,000
OUTPUT IMPEDANCE
vs. FREQUENCY
0.1
MAX492-18
FREQUENCY (kHz)
OUTPUT IMPEDANCE (
)
1
10
100
0.1
1
100
1,000
V
CM
= V
OUT
= 2.5V
____________________________Typical Operating Characteristics (continued)
(T
A
= +25C, V
CC
= 5V, V
EE
= 0V, unless otherwise noted.)
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
8
_______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(T
A
= +25C, V
CC
= 5V, V
EE
= 0V, unless otherwise noted.)
100
1
0.01
1
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
10
MAX492-19
FREQUENCY (kHz)
VOLTAGE-NOISE DENSITY (nV/
Hz)
0.1
10
INPUT REFERRED
5.0
0
0.01
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
R
L
= 10k
TO GND
A
V
= +1
2V
P-P
SIGNAL
80kHz LOWPASS FILTER
V
IN
50mV/div
V
OUT
50mV/div
V
CC
= +5V, A
V
= +1, R
L
= 10k
2
s/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
5.0
4.1
4.4 4.5 4.6
4.8 4.9
R
L
= 10k
R
L
= 100k
A
V
= +1
1kHz SINE
22kHz FILTER
R
L
TO GND
R
L
= 1k
R
L
= 2k
V
IN
50mV/div
V
OUT
50mV/div
V
CC
= +5V, A
V
= -1, R
L
= 10k
2
s/div
SMALL-SIGNAL TRANSIENT RESPONSE
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
_______________________________________________________________________________________
9
____________________________Typical Operating Characteristics (continued)
(T
A
= +25C, V
CC
= 5V, V
EE
= 0V, unless otherwise noted.)
V
IN
2V/div
V
OUT
2V/div
V
CC
= +5V, A
V
= -1, R
L
= 10k
50
s/div
LARGE-SIGNAL TRANSIENT RESPONSE
V
IN
2V/div
V
OUT
2V/div
V
CC
= +5V, A
V
= +1, R
L
= 10k
50
s/div
LARGE-SIGNAL TRANSIENT RESPONSE
______________________________________________________________Pin Description
Amplifier Output
OUT
--
Amplifier 2 Inverting Input
IN2-
6
Amplifier 2 Output
OUT2
7
Positive Power-Supply Pin. Connect to (+) terminal of power supply.
V
CC
8
Amplifier 3 Output
OUT3
--
Noninverting Input
IN+
--
Amplifier 1 Noninverting Input
IN1+
3
Negative Power-Supply Pin. Connect to ground or a negative voltage.
V
EE
4
Amplifier 2 Noninverting Input
IN2+
5
Amplifier 1 Inverting Input
IN1-
2
Inverting Input
IN-
--
Offset Null Input. Connect to a 10k
potentiometer for offset-voltage trimming.
Connect wiper to V
EE
(Figure 3).
NULL
--
Amplifier 1 Output
OUT1
1
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 Input
IN3-
--
Amplifier 3 Noninverting Input
IN3+
--
Amplifier 4 Noninverting Input
IN4+
--
9
10
12
--
--
--
Amplifier 4 Inverting Input
IN4-
--
Amplifier 4 Output
OUT4
--
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
V
EE
4
NULL
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 100k
load. 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 3.0V
p-p
, 1kHz sinusoid
centered at +1.5V. The output amplitude is approxi-
mately 2.95V
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 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 (500V max
at +25C), connect a 10k
trim potentiometer between
the two NULL pins (pins 1 and 5), with the wiper con-
nected to V
EE
(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
V
IN
V
OUT
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
T
he 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 1.7k
resistors in series
(Figure 4). The diodes limit the differential voltage
applied to the amplifiers' internal circuitry to no more
than V
F
, where V
F
is the diodes' forward-voltage drop
(about 0.7V at +25C).
Input bias current for the ICs (25nA typical) is speci-
fied for the small differential input voltages. For large
differential input voltages (exceeding V
F
), this protec-
tion circuitry increases the input current at IN+ and IN-:
(V
IN
+ - V
IN
- ) - V
F
Input Current = ----------------------
2 x 1.7k
For comparator applications requiring large differential
voltages (greater than V
F
), you can limit the input cur-
rent that flows through the diodes with external resistors
R1
V
OUT
R3 = R2
II
R1
R3
V
IN
R2
MAX49_
Figure 3a. Reducing Offset Error Due to Bias Current:
Inverting Configuration
R3
V
OUT
R3 = R2
II
R1
V
IN
R1
R2
MAX49_
MAX492
MAX494
MAX495
1.7k
1.7k
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 (k
)
CAPACITIVE LOAD (pF)
1000
UNSTABLE REGION
V
CC
= +5V
V
OUT
= V
CC
/2
R
L
TO V
EE
A
V
= +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 150A
per op amp, the MAX492/MAX494/MAX495 are well
suited for driving loads up to 1k
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 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.
10
s/div
V
IN
50mV/div
V
OUT
50mV/div
10
s/div
V
IN
50mV/div
V
OUT
50mV/div
10
s/div
V
IN
50mV/div
V
OUT
50mV/div
Figure 7c. MAX492 Voltage Follower with 500pF Load--
R
L
=
Figure 7a. MAX492 Voltage Follower with 500pF Load--
R
L
= 5k
Figure 7b. MAX492 Voltage Follower with 500pF Load--
R
L
= 20k
V
IN
50mV/div
V
OUT
50mV/div
10
s/div
Figure 6. MAX492 Voltage Follower with 1000pF Load
(R
L
=
)
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 100A. 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 (R
S
) 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 (R
L
100k
), while Figure 9b adds a 47
isolation resistor.
MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
______________________________________________________________________________________
13
V
IN
50mV/div
V
OUT
50mV/div
10
s/div
V
IN
50mV/div
V
OUT
50mV/div
10
s/div
MAX495
V
OUT
V
CC
2
3
1k
1k
+5V
7
4
6
MAX49_
V
OUT
V
IN
C
L
R
S
Figure 10. Power-Up Test Configuration
Figure 9b. Driving a 10,000pF Capacitive Load with a 47
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 150A 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 V
CC
, the output settles in approximately 4s
for V
CC
= +3V (Figure 11a) or 10s for V
CC
= +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 1F capacitor in parallel with a
0.1F 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 200V. This results in an
error at the ADC input of 400V, 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
______________________________________________________________________________________
V
CC
1V/div
V
OUT
500mV/div
5
s/div
V
CC
2V/div
V
OUT
1V/div
5
s/div
Figure 11b. Power-Up Settling Time (V
CC
= +5V)
Figure 11a. Power-Up Settling Time (V
CC
= +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 V
EE
OUT2
V
CC
V
CC
V
EE
IN1+
IN1-
IN2-
IN2+
0.068"
(1.728mm)
0.069"
(1.752mm)
OUT1
V
CC
MAX492
OUT
V
CC
IN-
NULL1
NULL2
0.056"
(1.422mm)
0.055"
(1.397mm)
IN+
V
EE
MAX495
* Dice are specified at T
A
= +25C, DC parameters only.
TOP VIEW
14
13
12
11
10
9
8
1
2
3
4
5
6
7
OUT4
IN4-
IN4+
V
EE
V
CC
IN1+
IN1-
OUT1
MAX494
IN3+
IN3-
OUT3
OUT2
IN2-
IN2+
DIP/SO
PART
MAX494
CPD
MAX494CSD
MAX494EPD
-40C to +85C
0C to +70C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
14 Plastic DIP
14 SO
14 Plastic DIP
MAX494ESD
MAX494MJD
-55C to +125C
-40C to +85C
14 SO
14 CERDIP
MAX495
CPA
MAX495CSA
MAX495CUA
0C to +70C
0C to +70C
0C to +70C
8 Plastic DIP
8 SO
8 MAX
MAX495C/D
MAX495EPA
-40C to +85C
0C to +70C
Dice*
8 Plastic DIP
MAX495ESA
-40C to +85C
8 SO
MAX495MJA
-55C to +125C
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
C
A1
B
DIM
A
A1
B
C
D
E
e
H
L
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
MAX
MICROMAX SMALL-OUTLINE
PACKAGE
0.65
0.0256
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
1.27
0.050
L
0-8
H
E
D
e
A
A1
C
0.101mm
0.004in.
B
PDF 
ZIP