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19-2272; Rev 0; 1/02
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
General Description
The single MAX4091, dual MAX4092, and quad MAX4094 operational amplifiers combine excellent DC accuracy with Rail-to-Rail(R) 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 130A of 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 12nV/Hz. In addition, these op amps can drive loads in excess of 2000pF. The precision performance of the MAX4091/MAX4092/ MAX4094 combined with their wide input and output dynamic range, low-voltage, single-supply operation, and very low supply current, make them an ideal choice for battery-operated equipment, industrial, and data acquisition and control applications. In addition, the MAX4091 is available in space-saving 5-pin SOT23, 8-pin MAX, and 8-pin SO packages. The MAX4092 is available in 8-pin MAX and SO packages, and the MAX4094 is available in 14-pin TSSOP and 14-pin SO packages. o Beyond-the-RailsTM Inputs o No Phase Reversal for Overdriven Inputs o 30V Offset Voltage o Rail-to-Rail Output Swing with 1k Load o Unity-Gain Stable with 2000pF Load o 165A (max) Quiescent Current Per Op Amp o 500kHz Gain-Bandwidth Product o High Voltage Gain (115dB) o High Common-Mode Rejection Ratio (90dB) and Power-Supply Rejection Ratio (100dB) o Temperature Range (-40C to +125C)
Features
o Low-Voltage, Single-Supply Operation (2.7V to 6V)
MAX4091/MAX4092/MAX4094
Ordering Information
PART MAX4091AUK-T MAX4091ASA MAX4091AUA MAX4092ASA MAX4092AUA MAX4094AUD MAX4094ASD TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 5 SOT23-5 8 SO 8 MAX 8 SO 8 MAX 14 TSSOP 14 SO
________________________Applications
Portable Equipment Battery-Powered Instruments Data Acquisition and Control Low-Voltage Signal Conditioning
Pin Configurations/Functional Diagrams
TOP VIEW OUT1 1 N.C. 1 IN- 2 IN+ 3 VEE 4 MAX/SO MAX4091 8 7 6 5 N.C. VCC OUT N.C. OUT 1 VEE 2 IN+ 3 SOT23 4 IN5 VCC OUT1 1 IN1- 2 IN1+ 3 VEE 4 MAX/SO IN1- 2 MAX4092 8 7 6 5 VCC OUT2 IN2IN2+ IN2- 6 OUT2 7 9 8 IN3OUT3 IN1+ 3 VCC 4 IN2+ 5 MAX4094 14 OUT4 13 IN412 IN4+ 11 VEE 10 IN3+
MAX4091
TSSOP/SO
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE) ....................................................7V Common-Mode Input Voltage..........(VCC + 0.3V) to (VEE - 0.3V) Differential Input Voltage .........................................(VCC - VEE) Input Current (IN+, IN-) ....................................................10mA Output Short-Circuit Duration OUT shorted to GND or VCC .................................Continuous Continuous Power Dissipation (TA = +70C) 5-Pin SOT23 (derate 7.1mW/C above +70C)...........571mW 8-Pin SO (derate 5.88mW/C above +70C)...............471mW 8-Pin MAX (derate 4.1mW/C above +70C) ............330mW 14-Pin SO (derate 8.33mW/C above +70C).............667mW 14-Pin TSSOP (derate 9.1mW/C above +70C) ........727mW Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25C.)
PARAMETER DC CHARACTERISTICS Supply Voltage Range Supply Current Input Offset Voltage Input Bias Current Input Offset Current Input Common-Mode Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio VCC ICC VOS IB IOS VCM CMRR PSRR Inferred from PSRR test VCM = VCC/2 VCC = 2.7V VCC = 5V 2.7 115 130 0.03 20 0.2 VEE - 0.05 71 86 83 81 91 78 87 83 97 84 90 100 105 105 105 90 115 115 110 100 15 130 15 80 500 60 10 0.20 69 210 70 220 mV mV dB 6.0 165 185 1.4 180 7 VCC + 0.05 V A mV nA nA V dB dB SYMBOL CONDITIONS MIN TYP MAX UNITS
VCM = VEE to VCC VCM = VEE to VCC VCM = VEE to VCC Inferred from CMRR test (VEE - 0.05V) VCM (VCC + 0.05V) 2.7V VCC 6V VCC = 2.7V, RL = 100k Sourcing 0.25V VOUT 2.45V Sinking
Large-Signal Voltage Gain (Note 1)
AVOL
VCC = 2.7V, RL = 1k 0.5V VOUT 2.2V
Sourcing Sinking
VCC = 5.0V, RL = 100k Sourcing 0.25V VOUT 4.75V Sinking VCC = 5.0V, RL = 1k 0.5V VOUT 4.5V Sourcing Sinking RL = 100k RL = 1k RL = 100k RL = 1k
Output Voltage Swing High (Note 1) Output Voltage Swing Low (Note 1) AC CHARACTERISTICS Gain-Bandwidth Product Phase Margin Gain Margin Slew Rate
VOH VOL
|VCC - VOUT| |VOUT - VEE|
RL = 100k, CL = 100pF RL = 100k, CL = 100pF RL = 100k, CL = 100pF RL = 100k, CL = 15pF
GBWP M SR
kHz degrees dB V/s
2
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Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = +25C.)
PARAMETER Input-Noise Voltage Density Input-Noise Current Density Noise Voltage (0.1Hz to 10Hz) Total Harmonic Distortion Plus Noise Capacitive-Load Stability Settling Time Power-On Time Op-Amp Isolation THD + N CLOAD tS tON f = 1kHz, RL = 10k, CL = 15pF, AV = 1, VOUT = 2VP-P AV = 1 To 0.1%, 2V step VCC = 0 to 3V step, VIN = VCC/2, AV = 1 f = 1kHz (MAX4092/MAX4094) SYMBOL eN f = 10kHz f = 10kHz CONDITIONS MIN TYP 12 1.5 16 0.003 2000 12 2 125 MAX UNITS nV/Hz pA/Hz VRMS % pF s s dB
MAX4091/MAX4092/MAX4094
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6V, VEE = GND, VCM = 0, VOUT = VCC/2, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25C.) (Note 2)
PARAMETER DC CHARACTERISTICS Supply Voltage Range Supply Current Input Offset Voltage Input Offset Voltage Tempco Input Bias Current Input Offset Current Input Common-Mode Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio VCC ICC VOS VOS/T IB IOS VCM CMRR PSRR VCM = VEE to VCC VCM = VEE to VCC Inferred from CMRR test (VEE - 0.05V) VCM (VCC + 0.05V) 2.7V VCC 6V VCC = 2.7V, RL = 100k 0.25V VOUT 2.45V Large-Signal Voltage Gain (Note 1) VCC = 2.7V, RL = 1k 0.5V VOUT 2.2V VCC = 5V, RL = 100k 0.25V VOUT 4.75V VCC = 5V, RL = 1k 0.5V VOUT 4.5V Output Voltage Swing High (Note 1) Output Voltage Swing Low (Note 1) VOH VOL Sourcing Sinking Sourcing Sinking Sourcing Sinking Sourcing Sinking RL = 100k RL = 1k RL = 100k RL = 1k VEE - 0.05 62 80 82 80 90 76 86 82 94 80 75 250 75 250 mV mV dB Inferred from PSRR test VCM = VCC/2 VCM = VEE to VCC 2 200 20 VCC + 0.05 VCC = 2.7V VCC = 5V 2.7 6.0 200 225 3.5 V A mV V/C nA nA V dB dB SYMBOL CONDITIONS MIN TYP MAX UNITS
AVOL
VCC - VOUT VOUT - VEE
Note 1: RL is connected to VEE for AVOL sourcing and VOH tests. RL is connected to VCC for AVOL sinking and VOL tests. Note 2: All specifications are 100% tested at TA = +25C. Specification limits over temperature (TA = TMIN to TMAX) are guaranteed by design, not production tested. _______________________________________________________________________________________ 3
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Typical Operating Characteristics
(VCC = 5V, VEE = 0, TA = +25C, unless otherwise noted.)
GAIN AND PHASE vs. FREQUENCY
MAX4091 toc01
GAIN AND PHASE vs. FREQUENCY
80 60 GAIN 40 GAIN (dB) 20 0 -20 -40 0.01 PHASE 60 0 -60 180 120 PHASE (DEGREES) 80 60 AV = 1000 NO LOAD
MAX4091 toc02
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
120 PHASE (DEGREES) 100 PSRR (dB) 80 60 40 20 VEE VCC VIN = 2.5V
MAX4091 toc03
180 120 60 0
GAIN 40 GAIN (dB) 20 0 -20 -40 0.01
CL = 470pF AV = 1000 RL =
140
PHASE -60 -120
-120 -180 1000 10,000
0 0.1 1 10 100 -180 1000 10,000 -20 0.01
0.1
1
10
100
0.1
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
CHANNEL ISOLATION vs. FREQUENCY
MAX4901 toc04
OFFSET VOLTAGE vs. TEMPERATURE
MAX4091 toc05
OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE
VCM = 0
80 60 OFFSET VOLTAGE (V) 40 20 0 -20 -40 -60 VCC = 6V VCC = 2.7V
MAX4091 toc06
140 VIN = 2.5V CHANNEL SEPARATION (dB) 120 100 80 60 40 20 0 0.01
160 140 OFFSET VOLTAGE (mV) 120 100 80 60 40 20 0
100
-80 -100
0.1
1
10
100
1000 10,000
-60 -40 -20 0
20 40 60 80 100 120 140
-1
0
1
2
3
4
5
6
7
FREQUENCY (kHz)
TEMPERATURE (C)
COMMON-MODE VOLTAGE (V)
COMMON-MODE REJECTION RATIO vs. TEMPERATURE
MAX4091 toc07
INPUT BIAS CURRENT vs. COMMON-MODE VOLTAGE
20 INPUT BIAS CURRENT (nA) 15 10 5 0 -5 -10 -15 -20 -25 0 1 2 3 4 5 6 VCC = 6V VCC = 2.7V
MAX4091 toc08
INPUT BIAS CURRENT vs. TEMPERATURE
30 INPUT BIAS CURRENT (nA) 20 10 0 -10 -20 -30 -40 -50 -25 0 25 50 75 100 125 VCM = 0 VCC = 6V VCC = 2.7V VCC = 6V
MAX4091 toc09
110 100 90 CMRR (dB) 80 70 60 50 -60 -40 -20 0 VCM = -0.2V TO +5.2V VCM = -0.3V TO +5.3V VCM = -0.4V TO +5.4V VCM = 0 TO 5V VCM = -0.1V TO +5.1V
25
40 VCM = VCC
20 40 60 80 100 120 140
TEMPERATURE (C)
COMMON-MODE VOLTAGE (V)
TEMPERATURE (C)
4
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Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA = +25C, unless otherwise noted.)
MAX4091/MAX4092/MAX4094
SUPPLY CURRENT PER AMPLIFIER vs. TEMPERATURE
MAX4091 toc10
SUPPLY CURRENT PER AMPLIFIER vs. SUPPLY VOLTAGE
MAX4091 toc11
LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE
RL = 10k9 110 100 GAIN (dB) 90 80 70 60 50 VCC = 6V RL TO VEE 0 100 400 200 300 VCC - VOUT (mV) 500 600 RL = 1M9 RL = 100k9 RL = 1k9
MAX4091 toc12
220 200 SUPPLY CURRENT PER AMP (A) 180 160 140 120 100 80 60 40 20 0 -50 -25 0 25 50 75 100 VCC = 2.7V VCC = 5V VOUT = VCM = VCC/2
200 SUPPLY CURRENT PER AMP (A) 180 160 140 120 100 80 60 40
120
125
1
2
3
4
5
6
TEMPERATURE (C)
SUPPLY VOLTAGE (V)
LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE
MAX4091 toc13
LARGE-SIGNAL GAIN vs. TEMPERATURE
115 LARGE-SIGNAL GAIN (dB) 110 105 100 95 90 85 80 RL TO VEE VCC = 2.7V VCC = 6V RL = 1kW, 0.5V < VOUT < (VCC - 0.5V) RL TO VCC
MAX4091 toc14
LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE
110 100 GAIN (dB) 90 80 70 60 50 VCC = 6V RL TO VCC 0 100 200 300 400 500 600 RL = 1k9 RL = 10k9 RL = 1M9 RL = 100k9
MAX4091 toc15
120 RL = 1M9 110 100 GAIN (dB) 90 80 70 60 50 0 100 400 200 300 VCC - VOUT (mV) 500 VCC = 2.7V RL TO VEE RL = 100k9 RL = 10k9 RL = 1k9
120
120
600
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (C)
VOUT (mV)
LARGE-SIGNAL GAIN vs. OUTPUT VOLTAGE
MAX4091 toc16
LARGE-SIGNAL GAIN vs. TEMPERATURE
MAX4091 toc17
MINIMUM OUTPUT VOLTAGE vs. TEMPERATURE
200 180 MINIMUM VOUT (nV) 160 140 120 100 80 60 VCC = 6V, RL = 100kW VCC = 2.7V, RL = 100kW -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 40 20 0 VCC = 2.7V, RL = 1kW RL TO VCC VCC = 6V, RL = 1kW
MAX4091 toc18
120 110 RL = 100k9 100 GAIN (dB) 90 80 70 60 50 0 100 200 300 400 VOUT (mV) 500 RL = 1k9 RL = 10k9 VCC = 2.7V RL TO VCC RL = 1M9
120 115 LARGE-SIGNAL GAIN (dB) 110 105 100 95 90 VCC = 2.7V 85 80 RL TO VEE RL = 100kW, 0.3V < VOUT < (VCC - 0.3V) RL TO VCC VCC = 6V
220
600
-60 -40 -20 0
20 40 60 80 100 120 140
TEMPERATURE (C)
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5
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA = +25C, unless otherwise noted.)
MAXIMUM OUTPUT VOLTAGE vs. TEMPERATURE
MAX4091 toc19
OUTPUT IMPEDANCE vs. FREQUENCY
VOLTAGE-NOISE DENSITY (nV/OHz) VCM = VOUT = 2.5V OUTPUT IMPEDANCE (9) 100
MAX40912 toc20
VOLTAGE-NOISE DENSITY vs. FREQUENCY
MAX4091 toc21
200 180 160 (VCC - VOUT) (mV) 140 120 100 80 60 40 20 0 VCC = 6V, RL = 100kW VCC = 2.7V, RL = 100kW RL TO VEE VCC = 6V, RL = 1kW VCC = 2.7V, RL = 1kW
1000
100
10
10
1
INPUT REFERRED 1
0.1 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
0.01
0.1
1
10
FREQUENCY (kHz)
CURRENT-NOISE DENSITY vs. FREQUENCY
MAX4091 toc22
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX4091 toc23
TOTAL HARMONIC DISTORTION PLUS NOISE vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
AV = 1 1kHz SINE 22kHz FILTER RL TO GND THD + N (%)
MAX4091 toc24
5.0 CURRENT-NOISE DENSITY (pA/Hz) 4.5 4.0 3.5
0.1 AV = 1 2VP-P SIGNAL 80kHz LOWPASS FILTER
0.1
RL = 1k9 RL = 2k9
2.5 2.0 1.5 1.0 0.5 0 0.01 0.1 1 10 FREQUENCY (kHz) INPUT REFERRED
THD + N (%)
3.0
0.01
0.01
RL = 10k9 TO GND
RL = 100k9 RL = 10k9 NO LOAD 0.001 10 100 1000 10,000 FREQUENCY (Hz) 0.001 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4091 toc25
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4091 toc26
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc27
VCC = 5V, AV = 1, RL = 10k VIN 50mV/div VIN 50mV/div
VCC = 5V, AV = -1, RL = 10k VIN 2V/div
VCC = 5V, AV = 1, RL = 10k
VOUT 50mV/div
VOUT 50mV/div
VOUT 2V/div
2s/div
2s/div
20s/div
6
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Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Typical Operating Characteristics (continued)
(VCC = 5V, VEE = 0, TA = +25C, unless otherwise noted.)
SINK CURRENT vs. OUTPUT VOLTAGE
MAX4091 toc29
MAX4091/MAX4092/MAX4094
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc28
SOURCE CURRENT vs. SUPPLY VOLTAGE
VDIFF = 100mV 25 OUTPUT CURRENT (mA) 20 15 10 5 0 VCC = 2.7V VCC = 6V
MAX4091 toc30
0 -2 -4 OUTPUT CURRENT (mA) VDIFF = 100mV
30
VCC = 5V, AV = -1, RL = 10k VIN 2V/div
-6 -8 -10 -12 -14 -16 -18 -20 VCC = 2.7V VCC = 6V
VOUT 2V/div
20s/div
0
0.5
1.0
1.5
2.0
2.5
3.0
1.0
2.0
3.0
4.0
5.0
6.0
OUTPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
Pin Description
PIN MAX4091 SOT23 1 2 3 4 5 -- -- -- -- -- -- -- -- -- -- -- -- -- MAX4091 SO/MAX 6 4 3 2 7 1, 5, 8 -- -- -- -- -- -- -- -- -- -- -- -- MAX4092 -- 4 -- -- 8 -- 1 2 3 5 6 7 -- -- -- -- -- -- MAX4094 -- 11 -- -- 4 -- 1 2 3 5 6 7 8 9 10 12 13 14 NAME OUT VEE IN+ INVCC N.C. OUT1 IN1IN1+ IN2+ IN2OUT2 OUT3 IN3IN3+ IN4+ IN4OUT4 Amplifier Output Negative Supply Noninverting Input Inverting Input Positive Supply No Connection. Not internally connected. Amplifier 1 Output Amplifier 1 Inverting Input Amplifier 1 Noninverting Input Amplifier 2 Noninverting Input Amplifier 2 Inverting Input Amplifier 2 Output Amplifier 3 Output Amplifier 3 Inverting Input Amplifier 3 Noninverting Input Amplifier 4 Noninverting Input Amplifier 4 Inverting Input Amplifier 4 Output FUNCTION
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7
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Detailed Description
The single MAX4091, dual MAX4092 and quad MAX4094 op amps combine excellent DC accuracy with rail-to-rail operation at both input and output. With their precision performance, wide dynamic range at low supply voltages, and very low supply current, these op amps are ideal for battery-operated equipment, industrial, and data acquisition and control applications. match the effective resistance seen at each input. Connect resistor R3 between the noninverting input and ground when using the op amp in an inverting configuration (Figure 2a); connect resistor R3 between the noninverting input and the input signal when using the op amp in a noninverting configuration (Figure 2b). Select R3 to equal the parallel combination of R1 and R2. High source resistances will degrade noise performance, due to the the input current noise (which is multiplied by the source resistance).
Applications Information
Rail-to-Rail Inputs and Outputs
The MAX4091/MAX4092/MAX4094's input commonmode range extends 50mV beyond the positive and negative supply rails, with excellent common-mode rejection. Beyond the specified common-mode range, the outputs are guaranteed not to undergo phase reversal or latchup. Therefore, the MAX4091/MAX4092/ MAX4094 can be used in applications with commonmode signals, at or even beyond the supplies, without the problems associated with typical op amps. The MAX4091/MAX4092/MAX4094's output voltage swings to within 15mV of the supplies with a 100k load. This rail-to-rail swing at the input and the output substantially increases the dynamic range, especially in low-supply-voltage applications. Figure 1 shows the input and output waveforms for the MAX4092, configured as a unity-gain noninverting buffer operating from a single 3V supply. The input signal is 3.0VP-P, a 1kHz sinusoid centered at 1.5V. The output amplitude is approximately 2.98VP-P.
Input Stage Protection Circuitry
The MAX4091/MAX4092/MAX4094 include internal protection circuitry that prevents damage to the precision input stage from large differential input voltages. This protection circuitry consists of back-to-back diodes between IN+ and IN- with two 1.7k resistors in series (Figure 3). The diodes limit the differential voltage applied to the amplifiers' internal circuitry to no more than VF, where VF is the diodes' forward-voltage drop (about 0.7V at +25C). Input bias current for the ICs (20nA) is specified for small differential input voltages. For large differential input voltages (exceeding VF), this protection circuitry increases the input current at IN+ and IN-: INPUT CURRENT = [(VIN + ) - (VIN - )] - VF 2 1.7k
Output Loading and Stability
Even with their low quiescent current of less than 130A per op amp, the MAX4091/MAX4092/MAX4094 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 unitygain voltage follower. The output impedance and a capacitive load form an RC network that adds a pole to the loop response and induces phase lag. If the pole frequency is low enough--as when driving a large capacitive load--the circuit phase margin is degraded, leading to either an under-damped pulse response or oscillation. The MAX4091/MAX4092/MAX4094 can drive capacitive loads in excess of 2000pF under certain conditions (Figure 4). When driving capacitive loads, the greatest potential for instability occurs when the op amp is sourcing approximately 200A. Even in this case, stability is maintained with up to 400pF of output capaci-
Input Offset Voltage
Rail-to-rail common-mode swing at the input is obtained by two complementary input stages in parallel, which feed a folded cascaded stage. The PNP stage is active for input voltages close to the negative rail, and the NPN stage is active for input voltages close to the positive rail. The offsets of the two pairs are trimmed. However, there is some residual mismatch between them. This mismatch results in a two-level input offset characteristic, with a transition region between the levels occurring at a common-mode voltage of approximately 1.3V above VEE. Unlike other rail-to-rail op amps, the transition region has been widened to approximately 600mV in order to minimize the slight degradation in CMRR caused by this mismatch. The input bias currents of the MAX4091/MAX4092/ MAX4094 are typically less than 20nA. The bias current flows into the device when the NPN input stage is active, and it flows out when the PNP input stage is active. To reduce the offset error caused by input bias current flowing through external source resistances,
8
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Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
tance. If the output sources either more or less current, stability is increased. These devices perform well with a 1000pF pure capacitive load (Figure 5). Figures 6a, 6b, and 6c show the performance with a 500pF load in parallel with various load resistors. To increase stability while driving large-capacitive loads, connect a pullup resistor to VCC at the output to decrease the current the amplifier must source. If the amplifier is made to sink current rather than source, stability is further increased. Frequency stability can be improved by adding an output isolation resistor (RS) to the voltage-follower circuit (Figure 7). This resistor improves the phase margin of the circuit by isolating the load capacitor from the op amp's output. Figure 8a shows the MAX4092 driving 5000pF (RL 100k), while Figure 8b adds a 47 isolation resistor. Because the MAX4091/MAX4092/MAX4094 have excellent stability, no isolation resistor is required, except in the most demanding applications. This is beneficial because an isolation resistor would degrade the lowfrequency performance of the circuit. MAX4094, it takes some time for the voltages on the supply pin and the output pin of the op amp to settle. Supply settling time depends on the supply voltage, the value of the bypass capacitor, the output impedance of the incoming supply, and any lead resistance or inductance between components. Op amp settling time depends primarily on the output voltage and is slewrate limited. With the noninverting input to a voltage follower held at midsupply (Figure 9), when the supply steps from 0 to VCC, the output settles in approximately 2s for VCC = 3V (Figure 10a) and 8s for VCC = 5V (Figure 10b).
MAX4091/MAX4092/MAX4094
Power Supplies and Layout
The MAX4091/MAX4092/MAX4094 operate from a single 2.7V to 6V power supply, or from dual supplies of 1.35V to 3V. For single-supply operation, bypass the power supply with a 0.1F capacitor. If operating from dual supplies, bypass each supply to ground. Good layout improves performance by decreasing the amount of stray capacitance at the op amp's inputs and output. To decrease stray capacitance, minimize both trace lengths and resistor leads and place external components close to the op amp's pins.
Power-Up Settling Time
The MAX4091/MAX4092/MAX4094 have a typical supply current of 130A per op amp. Although supply current is already low, it is sometimes desirable to reduce it further by powering down the op amp and associated ICs for periods of time. For example, when using a MAX4092 to buffer the inputs of a multi-channel analogto-digital converter (ADC), much of the circuitry could be powered down between data samples to increase battery life. If samples are taken infrequently, the op amps, along with the ADC, may be powered down most of the time. When power is reapplied to the MAX4091/MAX4092/
Chip Information
MAX4091 TRANSISTOR COUNT: 168 MAX4092 TRANSISTOR COUNT: 336 MAX4094 TRANSISTOR COUNT: 670 PROCESS: Bipolar
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9
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Test Circuits/Timing Diagrams
VCC = 3V VEE = 0 VIN 1V/div R1 VIN
R2
MAX409_
VOUT 1V/div R3 R3 = R2 II R1
VOUT
200s/div
Figure 1. Rail-to-Rail Input and Output Operation
Figure 2a. Reducing Offset Error Due to Bias Current: Inverting Configuration
R3 VIN IN+
1.7k
TO INTERNAL CIRCUITRY
MAX4091 MAX4092 MAX4094
MAX409_
R2 R3 = R2 II R1 R1
VOUT
IN- 1.7k
TO INTERNAL CIRCUITRY
Figure 2b. Reducing Offset Error Due to Bias Current: Noninverting Configuration
Figure 3. Input Stage Protection Circuitry
10
______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Test Circuits/Timing Diagrams (continued)
MAX4091/MAX4092/MAX4094
10,000 RL = UNSTABLE REGION VIN 50mV/div
CAPACITIVE LOAD (pF)
1000
VCC = 5V VOUT = VCC/2 RL TO VEE AV = 1 100 1 10 RESISTIVE LOAD (k) 100
VOUT 50mV/div
10s/div
Figure 4. Capacitive-Load Stable Region Sourcing Current
Figure 5. MAX4092 Voltage Follower with 1000pF Load
RL = 5k VIN 50mV/div VIN 50mV/div
RL = 20k
VOUT 50mV/div
VOUT 50mV/div
10s/div
10s/div
Figure 6a. MAX4092 Voltage Follower with 500pF Load (RL = 5k)
Figure 6b. MAX4092 Voltage Follower with 500pF Load (RL = 20k)
______________________________________________________________________________________
11
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Test Circuits/Timing Diagrams (continued)
RL = VIN 50mV/div
RS
MAX409_
VIN
VOUT 50mV/div
VOUT CL
10s/div
Figure 6c. MAX4092 Voltage Follower with 500pF Load (RL = )
Figure 7. Capacitive-Load Driving Circuit
VIN 50mV/div
VIN 50mV/div
VOUT 50mV/div
VOUT 50mV/div
10s/div
10s/div
Figure 8a. Driving a 5000pF Capacitive Load
Figure 8b. Driving a 5000pF Capacitive Load with a 47 Isolation Resistor
12
______________________________________________________________________________________
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Test Circuits/Timing Diagrams (continued)
MAX4091/MAX4092/MAX4094
5V
VCC 2 1k
VIN 1V/div
7 6
MAX409_
3 1k 4
VOUT
VOUT 500mV/div
5s/div
Figure 9. Power-Up Test Configuration
Figure 10a. Power-Up Settling Time (VCC = +3V)
VIN 2V/div
VOUT 1V/div 5s/div
Figure 10b. Power-Up Settling Time (VCC = +5V)
______________________________________________________________________________________
13
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Package Information
SOT5L.EPS
14
______________________________________________________________________________________
8LUMAXD.EPS
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
Package Information (continued)
SOICN.EPS
MAX4091/MAX4092/MAX4094
______________________________________________________________________________________
15
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps MAX4091/MAX4092/MAX4094
Package Information (continued)
TSSOP,NO PADS.EPS
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 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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