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.
19-0265; Rev 2; 9/96
General Description Features
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 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-
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 1k Load
Drives Large Capacitive Loads
MAX495 Available in µMAX Package—8-Pin SO
cations. The MAX492/MAX494/MAX495 are available in Ordering Information
DIP and SO packages in the industry-standard op-amp
PART | TEMP. RANGE | PIN-PACKAGE | |
MAX492CPA | 0°C to | +70°C | 8 Plastic DIP |
MAX492CSA | 0°C to | +70°C | 8 SO |
MAX492C/D | 0°C to | +70°C | Dice* |
MAX492EPA | -40°C to | +85°C | 8 Plastic DIP |
MAX492ESA | -40°C to | +85°C | 8 SO |
MAX492MJA | -55°C to | +125°C | 8 CERDIP |
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
Ordering Information continued at end of data sheet.
*Dice are specified at TA = +25°C, DC parameters only.
Typical Operating Circuit Pin Configurations
+5V 1 VDD 10k MAX187 2 7 (ADC) 6 DOUT 6 2 AIN SCLK 8 SERIAL MAX495 7 INTERFACE ANALOG 3 CS INPUT 4 SHDN 3 10k REF 4 4.096V GND 5 INPUT SIGNAL CONDITIONING FOR LOW-VOLTAGE ADC |
TOPVIEW OUT1 1 8 VCC IN1- 2 7 OUT2 IN1+ 3 6 IN2- VEE 4 5 IN2+ MAX492 DIP/SO NULL 1 8 N.C. IN1- 2 MAX495 7 VCC IN1+ 3 6 OUT VEE 4 5 NULL DIP/SO/MAX PinConfigurations continuedatendof datasheet. |
Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
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-, 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
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.
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = +25°C, unless otherwise noted.)
PARAMETER | CONDITIONS | MIN | TYP | MAX | UNITS | |
Input Offset Voltage | VCM = VEE to VCC | ±200 ±500 | µV | |||
Input Bias Current | VCM = VEE to VCC | ±25 ±60 | nA | |||
Input Offset Current | VCM = VEE to VCC | ±0.5 ±6 | nA | |||
Differential Input Resistance | 2 | M | ||||
Common-Mode Input Voltage Range | VEE - 0.25 | VCC + 0.25 | V | |||
Common-Mode Rejection Ratio | (VEE - 0.25V) VCM (VCC + 0.25V) | 74 | 90 | dB | ||
Power-Supply Rejection Ratio | VCC = 2.7V to 6V | 88 | 110 | dB | ||
Large-Signal Voltage Gain (Note 1) | VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V | Sourcing | 90 | 104 | dB | |
Sinking | 90 | 102 | ||||
VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V | Sourcing | 94 | 105 | |||
Sinking | 78 | 90 | ||||
VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V | Sourcing | 98 | 108 | |||
Sinking | 92 | 100 | ||||
VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V | Sourcing | 98 | 110 | |||
Sinking | 86 | 98 | ||||
Output Voltage Swing (Note 1) | RL = 100k | VOH | VCC - 0.075 VCC - 0.04 | V | ||
VOL | VEE + 0.04 VEE + 0.075 | |||||
RL = 1k | VOH | VCC - 0.20 | VCC - 0.15 | |||
VOL | VEE + 0.15 VEE + 0.20 | |||||
Output Short-Circuit Current | 30 | mA | ||||
Operating Supply Voltage Range | 2.7 | 6.0 | V | |||
Supply Current (per amplifier) | VCM = VOUT = VCC / 2 | VCC = 2.7V | 135 150 | µA | ||
VCC = 5V | 150 170 |
AC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, TA = +25°C, unless otherwise noted.)
PARAMETER | CONDITIONS | MIN TYP MAX | UNITS |
Gain-Bandwidth Product | RL = 100k, CL = 100pF | 500 | kHz |
Phase Margin | RL = 100k, CL = 100pF | 60 | degrees |
Gain Margin | RL = 100k, CL = 100pF | 10 | dB |
Total Harmonic Distortion | RL = 10k, CL = 15pF, VOUT = 2Vp-p, AV = +1, f = 1kHz | 0.003 | % |
Slew Rate | RL = 100k, CL = 15pF | 0.20 | V/µs |
Time | To 0.1%, 2V step | 12 | µs |
Turn-On Time | VCC = 0V to 3V step, VIN = VCC / 2, AV = +1 | 5 | µs |
Input Noise-Voltage Density | f = 1kHz | 25 | nV/Hz |
Input Noise-Current Density | f = 1kHz | 0.1 | pA/Hz |
Amp-Amp Isolation | f = 1kHz | 125 | dB |
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = 0°C to +70°C, unless otherwise noted.)
PARAMETER | CONDITIONS | MIN TYP MAX | UNITS | |
Input Offset Voltage | VCM = VEE to VCC | ±650 | µV | |
Input Offset Voltage Tempco | ±2 | µV/°C | ||
Input Bias Current | VCM = VEE to VCC | ±75 | nA | |
Input Offset Current | VCM = VEE to VCC | ±6 | nA | |
Common-Mode Input Voltage Range | VEE - 0.20 VCC + 0.20 | V | ||
Common-Mode Rejection Ratio | (VEE - 0.20) VCM (VCC + 0.20) | 72 | dB | |
Power-Supply Rejection Ratio | VCC = 2.7V to 6V | 86 | dB | |
Large-Signal Voltage Gain (Note 1) | VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V | Sourcing | 88 | dB |
Sinking | 84 | |||
VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V | Sourcing | 92 | ||
Sinking | 76 | |||
VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V | Sourcing | 92 | ||
Sinking | 88 | |||
VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V | Sourcing | 96 | ||
Sinking | 82 | |||
Output Voltage Swing (Note 1) | RL = 100k | VOH | VCC - 0.075 | V |
VOL | VEE + 0.075 | |||
RL = 1k | VOH | VCC - 0.20 | ||
VOL | VEE + 0.20 | |||
Operating Supply Voltage Range | 2.7 6.0 | V | ||
Supply Current (per amplifier) | VCM = VOUT = VCC / 2 | VCC = 2.7V | 175 | µA |
VCC = 5V | 190 |
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER | CONDITIONS | MIN TYP MAX | UNITS | |
Input Offset Voltage | VCM = VEE to VCC | ±950 | µV | |
Input Offset Voltage Tempco | ±2 | µV/°C | ||
Input Bias Current | VCM = VEE to VCC | ±100 | nA | |
Input Offset Current | VCM = VEE to VCC | ±8 | nA | |
Common-Mode Input Voltage Range | VEE - 0.15 VCC + 0.15 | V | ||
Common-Mode Rejection Ratio | (VEE - 0.15) VCM (VCC + 0.15) | 68 | dB | |
Power-Supply Rejection Ratio | VCC = 2.7V to 6V, VCM = 0V | 84 | dB | |
Large-Signal Voltage Gain (Note 1) | VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V | Sourcing | 86 | dB |
Sinking | 84 | |||
VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V | Sourcing | 92 | ||
Sinking | 76 | |||
VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V | Sourcing | 92 | ||
Sinking | 86 | |||
VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V | Sourcing | 96 | ||
Sinking | 80 | |||
Output Voltage Swing (Note 1) | RL = 100k | VOH | VCC - 0.075 | V |
VOL | VEE + 0.075 | |||
RL = 1k | VOH | VCC - 0.20 | ||
VOL | VEE + 0.20 | |||
Operating Supply-Voltage Range | 2.7 6.0 | V | ||
Supply Current (per amplifier) | VCM = VOUT = VCC / 2 | VCC = 2.7V | 185 | µA |
VCC = 5V | 200 |
DC ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0V, VOUT = VCC / 2, TA = -55°C to +125°C, unless otherwise noted.)
PARAMETER | CONDITIONS | MIN TYP MAX | UNITS | |
Input Offset Voltage | VCM = VEE to VCC | ±1.2 | mV | |
Input Offset Voltage Tempco | ±2 | µV/°C | ||
Input Bias Current | VCM = VEE to VCC | ±200 | nA | |
Input Offset Current | VCM = VEE to VCC | ±10 | nA | |
Common-Mode Input Voltage Range | VEE - 0.05 VCC + 0.05 | V | ||
Common-Mode Rejection Ratio | (VEE - 0.05V) VCM (VCC + 0.05V) | 66 | dB | |
Power-Supply Rejection Ratio | VCC = 2.7V to 6V | 80 | dB | |
Large-Signal Voltage Gain (Note 1) | VCC = 2.7V, RL = 100k, VOUT = 0.25V to 2.45V | Sourcing | 82 | dB |
Sinking | 80 | |||
VCC = 2.7V, RL = 1k, VOUT = 0.5V to 2.2V | Sourcing | 90 | ||
Sinking | 72 | |||
VCC = 5.0V, RL = 100k, VOUT = 0.25V to 4.75V | Sourcing | 86 | ||
Sinking | 82 | |||
VCC = 5.0V, RL = 1k, VOUT = 0.5V to 4.5V | Sourcing | 94 | ||
Sinking | 76 | |||
Output Voltage Swing (Note 1) | RL = 100k | VOH | VCC - 0.075 | V |
VOL | VEE + 0.075 | |||
RL = 1k | VOH | VCC - 0.250 | ||
VOL | VEE + 0.250 | |||
Operating Supply-Voltage Range | 2.7 6.0 | V | ||
Supply Current (per amplifier) | VCM = VOUT = VCC / 2 | VCC = 2.7V | 200 | µA |
VCC = 5V | 225 |
Note 1: RL to VEE for sourcing and VOH tests; RL to VCC for sinking and VOL tests.
Typical Operating Characteristics
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
80
60
GAIN (dB)
40
20
0
-20
-40
GAINAND PHASE vs. FREQUENCY
H
P
GAIN
ASE
AV = +1000 NO LOAD
MAX492-01 180
120
PHASE (DEG)
60
0
-60
-120
-180
80
60
GAIN (dB)
40
20
0
-20
-40
GAINAND PHASE vs. FREQUENCY
GA
IN
P
HASE
CL = 470pF AV = +1000 RL =
MAX492-02 180
120
PHASE (DEG)
60
0
-60
-120
-180
140
120
100
PSRR (dB)
80
60
40
20
0
-20
POWER-SUPPLY REJECTIONRATIO vs. FREQUENCY
V
CC
MAX492-03
VEE
VIN = 2.5V
0.01
0.1 1
10 100 1000 10,000
0.01
0.1 1
10 100 1000 10,000
0.01
0.1 1
10 100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
140
CHANNEL SEPARATION (dB)
120
100
80
60
40
20
0
CHANNELSEPARATION vs. FREQUENCY
VIN = 2.5V
160
MAX492-04
140
OFFSET VOLTAGE (V)
120
100
80
60
40
20
0
OFFSET VOLTAGE vs. TEMPERATURE
MAX492-05
120
110
CMRR (dB)
100
90
80
70
60
COMMON-MODEREJECTIONRATIO vs. TEMPERATURE
MAX492-06
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
VCM = 0V | |||||||||
0.01
0.1 1
10 100 1000 10,000
-60 -40 -20 0
20 40
60 80 100 120 140
-60 -40 -20 0
20 40
60 80 100 120 140
FREQUENCY (kHz)
TEMPERATURE (C)
TEMPERATURE (C)
INPUT BIASCURRENT vs. COMMON-MODE VOLTAGE
20
MAX492-07
125
INPUT BIASCURRENT vs. TEMPERATURE
MAX492-08
220
SUPPLY CURRENT PERAMPLIFIER vs. TEMPERATURE
15
INPUT BIAS CURRENT (nA)
10
5
0
-5
-10
-15
-20
-25
-30
VCC= 6V
VCC
= 2.7V
100
INPUT BIAS CURRENT (nA)
75
50
25
0
-25
-50
-75
-100
-125
MAX492-09
VCM = VCC
VCM = 0
VCC= 6V
VCC= 2.7V
VCC= 6V
200
SUPPLY CURRENT PEROP AMP (A)
180
160
140
120
100
80
60
40
20
0
VOUT = VCM = VCC/2
VCC= 5V
VCC= 2.7V
0 1 2 3
4 5 6 7
-60 -40 -20 0
20 40 60
80 100 120 140
-60 -40 -20 0
20 40 60
80 100 120 140
VCM (V)
TEMPERATURE (C)
TEMPERATURE (C)
Typical Operating Characteristics (continued)
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
120
110
GAIN (dB)
100
90
80
70
60
50
LARGE-SIGNALGAIN vs. OUTPUT VOLTAGE
RL = 10k
RL = 1M RL = 100k
RL = 1k
V
VCC= +6 RL TOVEE
120
MAX492-10
110
GAIN (dB)
100
90
80
70
60
50
LARGE-SIGNALGAIN vs. OUTPUT VOLTAGE
RL = 1M
RL = 100k RL = 10k
RL = 1k
VCC= +2.7V RL TOVEE
120
MAX492-11
LARGE-SIGNAL GAIN (dB)
115
110
105
100
95
90
85
80
LARGE-SIGNALGAIN vs. TEMPERATURE
MAX492-12
RL = 1k, 0.5V < VOUT < (VCC- 0.5V) RL TOVCC
VCC= +2.7V
VCC= +6V
RL TOVEE
0 100
200
300 400
500
600
0 100
200
300 400
500
600
-60 -40 -20 0 20
40 60 80 100 120 140
VCC- VOUT (mV)
VCC- VOUT (mV)
TEMPERATURE (C)
120
110
GAIN (dB)
100
90
80
70
LARGE-SIGNALGAIN vs. OUTPUT VOLTAGE
RL = 1M RL = 100k
RL = 1k RL = 10k
120
MAX492-13
110
GAIN (dB)
100
90
80
70
LARGE-SIGNALGAIN vs. OUTPUT VOLTAGE
RL = 1M
RL = 100k
RL = 1k RL = 10k
120
MAX492-14
LARGE-SIGNAL GAIN (dB)
115
110
105
100
95
90
LARGE-SIGNALGAIN vs. TEMPERATURE
MAX492-15
RL = 100k, 0.3V < VOUT < (VCC- 0.3V) RL TOVCC
VCC= +6V
RL TOVEE
60 VCC= +6V 60
RL TOVCC
50 50
VCC= +2.7V 85
RL TOVCC
80
VCC= +2.7V
0 100
200 300 400
500
600
0 100
200 300 400
500
600
-60 -40 -20 0 20
40 60 80 100 120 140
VOUT (mV)
VOUT (mV)
TEMPERATURE (C)
220
200
MINIMUM OUTPUT VOLTAGE vs. TEMPERATURE
RL TOVCC
200
MAX492-16
180
MAXIMUM OUTPUT VOLTAGE vs. TEMPERATURE
RL TOVEE
1000
OUTPUT IMPEDANCE vs. FREQUENCY
VCM = VOUT = 2.5
MAX492-18
V
180
VOUT MIN (mV)
160
140
120
100
80
VCC= 6V, RL = 1k
VCC= 2.7V, RL = 1k
160
(VCC- VOUT) (mV)
140
120
100
80
VCC
= 6V, RL = 1k
VCC= 2.7V, RL = 1k
MAX492-17
100
OUTPUT IMPEDANCE ( )
10
60 VCC
40
20
0
= 6V, RL = 100k
VCC= 2.7V, RL = 100k
60 VCC= 6V, RL = 100k
40 VCC= 2.7V, RL = 100k
20
0
1
0.1
-60 -40 -20 0
20 40 60 80 100 120140
-60 -40 -20 0
20 40 60 80 100 120140
0.01
0.1 1
10 100 1,000 10,000
TEMPERATURE (C)
TEMPERATURE (C)
FREQUENCY (kHz)
Typical Operating Characteristics (continued)
MAX492-19
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
VOLTAGE-NOISE DENSITY (nV/Hz)
100
10
1
VOLTAGE-NOISEDENSITY vs. FREQUENCY
INPUT REFERRED
5.0
CURRENT-NOISE DENSITY (pA/Hz)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
CURRENT-NOISEDENSITY vs. FREQUENCY
INPUT RE | FE | RRED | ||||||||||||
MAX492-20
0.01
0.1
1 10
0.01
0.1
1 10
FREQUENCY (kHz)
FREQUENCY (kHz)
0.1
THD + NOISE (%)
0.01
0.001
TOTALHARMONICDISTORTION + NOISE vs. FREQUENCY
AV
=
+1
2V
R
E
LT
FI
PASS
LO
z
kH
80
L
NA
IG
S
P-P
MAX492-21
W
RL = 10k TOGND
NO LOAD
0.1
THD + NOISE (%)
0.01
0.001
TOTALHARMONICDISTORTION + NOISE vs. PEAK-TO-PEAKSIGNALAMPLITUDE
MAX492-22
AV = +1 1kHz SINE
22kHz FILTER
RL TOGND RL = 1k
RL = 2k
RL = 100k
RL = 10k
10 100
1000
10,000
4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0
FREQUENCY (Hz)
PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
SMALL-SIGNAL TRANSIENT RESPONSE SMALL-SIGNAL TRANSIENT RESPONSE
VIN
50mV/div
VOUT
50mV/div
VIN
50mV/div
VOUT
50mV/div
2s/div VCC=+5V,AV=+1,RL=10k
2s/div VCC=+5V,AV= -1,RL=10k
Typical Operating Characteristics (continued)
(TA = +25°C, VCC = 5V, VEE = 0V, unless otherwise noted.)
LARGE-SIGNAL TRANSIENT RESPONSE LARGE-SIGNAL TRANSIENT RESPONSE
VIN
2V/div
VOUT
2V/div
VIN
2V/div
VOUT
2V/div
50s/div VCC=+5V,AV=+1,RL=10k
50s/div VCC=+5V,AV= -1,RL=10k
Pin Description
PIN | NAME | FUNCTION | ||
MAX492 | MAX494 | MAX495 | ||
1 | 1 | — | OUT1 | Amplifier 1 Output |
— | — | 1, 5 | NULL | Offset Null Input. Connect to a 10k potentiometer for offset-voltage trimming. Connect wiper to VEE (Figure 3). |
— | — | 2 | IN- | Inverting Input |
2 | 2 | — | IN1- | Amplifier 1 Inverting Input |
— | — | 3 | IN+ | Noninverting Input |
3 | 3 | — | IN1+ | Amplifier 1 Noninverting Input |
4 | 11 | 4 | VEE | Negative Power-Supply Pin. Connect to ground or a negative voltage. |
5 | 5 | — | IN2+ | Amplifier 2 Noninverting Input |
— | — | 6 | OUT | Amplifier Output |
6 | 6 | — | IN2- | Amplifier 2 Inverting Input |
7 | 7 | — | OUT2 | Amplifier 2 Output |
8 | 4 | 7 | VCC | Positive Power-Supply Pin. Connect to (+) terminal of power supply. |
— | 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 |
— | — | 8 | N.C. | No Connect. Not internally connected. |
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 3.0Vp-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 10k trim 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 |
10k 1 NULL MAX495 4 5 VEE NULL |
Figure 1. Rail-to-Rail Input and Output (Voltage Follower Circuit, VCC = +3V, VEE = 0V)
Figure 2. Offset Null Circuit
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 1.7k resistors in series
R2 R1 VIN VOUT MAX49_ R3 R3=R2 IIR1 |
Figure 3a. Reducing Offset Error Due to Bias Current: Inverting Configuration
R3 VIN VOUT MAX49_ R2 R3=R2 IIR1 R1 |
Figure 3b. Reducing Offset Error Due to Bias Current: Noninverting Configuration
(Figure 4). 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 (±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 1.7k
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
MAX492 MAX494 1.7k TOINTERNAL MAX495 IN+ CIRCUITRY IN– TOINTERNAL 1.7k CIRCUITRY |
1000
CAPACITIVE LOAD (pF)
MAX492-FG 04
Figure 4. Input Stage Protection Circuitry
10,000
UNSTABLE REGION
100
1
10
RESISTIVE LOAD (k)
100
VCC= +5V VOUT = VCC/2 RL TOVEE AV = +1
Figure 5. Capacitive-Load Stable Region Sourcing Current
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 1k while maintaining DC accuracy. Stability while driving heavy capacitive loads is another key advantage over comparable CMOS rail- to-rail op amps.
VIN 50mV/div VOUT 50mV/div 10s/div |
Figure 6. MAX492 Voltage Follower with 1000pF Load (RL = )
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.
VIN 50mV/div VOUT 50mV/div 10s/div |
Figure 7b. MAX492 Voltage Follower with 500pF Load— RL = 20k
VIN 50mV/div VOUT 50mV/div 10s/div |
VIN 50mV/div VOUT 50mV/div 10s/div |
Figure 7a. MAX492 Voltage Follower with 500pF Load— RL = 5k
Figure 7c. MAX492 Voltage Follower with 500pF 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.
RS MAX49_ VOUT CL VIN |
Figure 8. Capacitive-Load Driving Circuit
VIN 50mV/div VOUT 50mV/div 10s/div |
Figure 9a. Driving a 10,000pF Capacitive Load
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 100k), while Figure 9b adds a 47 isolation resistor.
VIN 50mV/div VOUT 50mV/div 10s/div |
Figure 9b. Driving a 10,000pF Capacitive Load with a 47 Isolation Resistor
+5V VCC 2 1k 7 6 VOUT MAX495 3 4 1k |
Figure 10. Power-Up Test Configuration
VCC 1V/div VOUT 500mV/div 5s/div |
VCC 2V/div VOUT 1V/div 5s/div |
Figure 11a. Power-Up Settling Time (VCC = +3V) Figure 11b. Power-Up Settling Time (VCC = +5V)
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.
_Ordering Information (continued) Chip Topographies
PART | TEMP. RANGE | PIN-PACKAGE | |
MAX494CPD | 0°C to | +70°C | 14 Plastic DIP |
MAX494CSD | 0°C to | +70°C | 14 SO |
MAX494EPD | -40°C to | +85°C | 14 Plastic DIP |
MAX494ESD | -40°C to | +85°C | 14 SO |
MAX494MJD | -55°C to | +125°C | 14 CERDIP |
MAX495CPA | 0°C to | +70°C | 8 Plastic DIP |
MAX495CSA | 0°C to | +70°C | 8 SO |
MAX495CUA | 0°C to | +70°C | 8 µMAX |
MAX495C/D | 0°C to | +70°C | Dice* |
MAX495EPA | -40°C to | +85°C | 8 Plastic DIP |
MAX495ESA | -40°C to | +85°C | 8 SO |
MAX495MJA | -55°C to | +125°C | 8 CERDIP |
MAX492
IN1+ IN1-
VCC
VEE
OUT1
0.068"
(1. 728mm) VCC
* Dice are specified at TA = +25°C, DC parameters only.
VCC
IN2+
IN2-
OUT2
0.069"
(1. 752mm)
Pin Configurations (continued)
IN-
IN+
NULL1
VEE
MAX495
NULL2
VCC
0.056"
(1. 422mm) OUT
TOPVIEW OUT1 1 14 OUT4 IN1- 2 13 IN4- IN1+ 3 12 IN4+ VCC 4 MAX494 11 VEE IN2+ 5 10 IN3+ IN2- 6 9 IN3- OUT2 7 8 OUT3 DIP/SO |
0.055"
(1. 397mm)
TRANSISTOR COUNT: 134 (single MAX495)
268 (dual MAX492)
536 (quad MAX494) SUBSTRATE CONNECTED TO VEE
Package Information
DIM | INCHES | MILLIMETERS | |||||||||||
MIN | MAX | MIN | MAX | ||||||||||
C | | A | 0.036 | 0.044 | 0.91 | 1.11 | |||||||
A1 | 0.004 | 0.008 | 0.10 | 0.20 | |||||||||
B | 0.010 | 0.014 | 0.25 | 0.36 | |||||||||
A | |||||||||||||
0.101mm | C | 0.005 | 0.007 | 0.13 | 0.18 | ||||||||
D | 0.116 | 0.120 | 2.95 | 3.05 | |||||||||
| e |
| 0.004 in | ||||||||||
E | 0.116 | 0.120 | 2.95 | 3.05 | |||||||||
B | A1 | L | |||||||||||
e | 0.0 | 256 | 0. | 65 | |||||||||
H | 0.188 | 0.198 | 4.78 | 5.03 | |||||||||
L | 0.016 | 0.026 | 0.41 | 0.66 | |||||||||
| 0° | 6° | 0° | 6° | |||||||||
D | E | H | 8-PIN MAX MICROMAX SMALL-OUTLINE PACKAGE | 21-0036D |
e | D | B | A1 | A | 0.101mm 0.004in. | 0°-8° C L | DIM | INCHES | MILLIMETERS | |||||
MIN | MAX | MIN | MAX | |||||||||||
A | 0.053 | 0.069 | 1.35 | 1.75 | ||||||||||
A1 | 0.004 | 0.010 | 0.10 | 0.25 | ||||||||||
B | 0.014 | 0.019 | 0.35 | 0.49 | ||||||||||
C | 0.007 | 0.010 | 0.19 | 0.25 | ||||||||||
E | 0.150 | 0.157 | 3.80 | 4.00 | ||||||||||
e | 0.050 | 1.27 | ||||||||||||
H | 0.228 | 0.244 | 5.80 | 6.20 | ||||||||||
L | 0.016 | 0.050 | 0.40 | 1.27 | ||||||||||
E | H | Narrow SO SMALL-OUTLINE PACKAGE | DIM | PINS | INCHES | MILLIMETERS | ||||||||
MIN | MAX | MIN | MAX | |||||||||||
D | 8 | 0.189 | 0.197 | 4.80 | 5.00 | |||||||||
D | 14 | 0.337 | 0.344 | 8.55 | 8.75 | |||||||||
D | 16 | 0.386 | 0.394 | 9.80 | 10.00 | |||||||||
(0.150 in.) | 21-0041A |
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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