View OP227AYMDA_120635.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

a
Dual, Low Noise, Low Offset Instrumentation Operational Amplifier OP227
PIN CONNECTIONS
NULL (A) NULL (A) -IN (A) +IN (A) V- (B) OUT (B) V+ (B)
1 2 3 14 13 12
FEATURES Excellent Individual Amplifier Parameters Low VOS, 80 V Max Offset Voltage Match, 80 V Max Offset Voltage Match vs. Temperature, 1 V/ C Max Stable VOS vs. Time, 1 V/M O Max Low Voltage Noise, 3.9 nV//Hz Max Fast, 2.8 V/ s Typ High Gain, 1.8 Million Typ High Channel Separation, 154 dB Typ
V+ (A) OUT (A) V- (A) +IN (B) -IN (B) NULL (B) NULL (B)
A
4 11
B
5 6 7 10 9 8
NOTE 1. DEVICE MAY BE OPERATED EVEN IF INSERTION IS REVERSED; THIS IS DUE TO INHERENT SYMMETRY OF PIN LOCATIONS OF AMPLIFIERS A AND B 2. V-(A) AND V-(B) ARE INTERNALLY CONNECTED VIA SUBSTRATE RESISTANCE
GENERAL DESCRIPTION
The OP227 is the first dual amplifier to offer a combination of low offset, low noise, high speed, and guaranteed amplifier matching characteristics in one device. The OP227, with a VOS match of 25 mV typical, a TCVOS match of 0.3 mV/C typical and a 1/f corner of only 2.7 Hz is an excellent choice for precision low noise designs. These dc characteristics, coupled with a slew rate of 2.8 V/ms typical and a small-signal bandwidth of 8 MHz typical, allow the designer to achieve ac performance previously unattainable with op amp based instrumentation designs. When used in a three op amp instrumentation configuration, the OP227 can achieve a CMRR in excess of 100 dB at 10 kHz. In addition, this device has an open-loop gain of 1.5 M typical with a 1 kW load. The OP227 also features an IB of 10 nA typical, an IOS of 7 nA typical, and guaranteed matching of input currents
between amplifiers. These outstanding input current specifications are realized through the use of a unique input current cancellation circuit which typically holds IB and IOS to 20 nA and 15 nA respectively over the full military temperature range. Other sources of input referred errors, such as PSRR and CMRR, are reduced by factors in excess of 120 dB for the individual amplifiers. DC stability is assured by a long-term drift application of 1.0 mV/month. Matching between channels is provided on all critical parameters including offset voltage, tracking of offset voltage versus temperature, noninverting bias current, CMRR, and power supply rejection ratio. This unique dual amplifier allows the elimination of external components for offset nulling and frequency compensation.
SIMPLIFIED SCHEMATIC
V+ Q6 R3 NULL R1* R2* Q21 Q23 R23 R24 Q24 R4 C2 Q22 C1 Q20 Q19 R9 OUTPUT NON INVERTING INPUT (+) INVERTING INPUT (-) Q3 Q11 Q12 Q26 R12 Q1A Q1B Q2B Q2A R5 C3 R11 C4 Q45 Q46
Q27
Q28 V-
*R1 AND R2 ARE PREMATURELY ADJUSTED AT WAFER TEST FOR MINIMUM OFFSET VOLTAGE.
REV. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2002
OP227-SPECIFICATIONS
Individual Amplifier Characteristics (V =
S
15 V, TA = 25 C, unless otherwise noted.)
Min OP227E Typ Max 20 0.2 7 10 80 1.0 35 40 0.20 Min OP227G Typ Max 60 0.4 12 15 0.09 180 2.0 75 80 0.28 Unit mV mV/MO nA nA mV p-p
Parameter INPUT OFFSET VOLTAGE LONG-TERM VOS STABILITY INPUT OFFSET CURRENT INPUT BIAS CURRENT INPUT NOISE VOLTAGE INPUT NOISE VOLTAGE DENSITY
Symbol VOS VOS/Time IOS IB en p-p
Conditions Note 1 Notes 2,4
0.1 Hz to 10 Hz Notes 3,5 fO = 10 Hz3 fO = 30 Hz3 fO = 1000 Hz3 fO = 10 Hz3, 6 fO = 30 Hz3, 6 fO = 1000 Hz3, 6 Note 7 1.3 11.0 VCM = 11 V VS = 4 V to 18 V RL 2 kW, VO = 10 V RL 600 kW, VO = 10 V RL RL RL 2 kW 600 W 2 kW4 114
0.08
en
3.5 3.1 3.0 1.7 1.0 0.4 6 3 12.3 126
6.0 4.7 3.9 4.5 2.5 0.7 0.7 11.0 100
3.8 3.3 3.2 1.7 1.0 0.4 4 2 12.3 120
9.0 5.9 4.6
nV/ Hz nV/ Hz nV/ Hz pA/ Hz pA/ Hz pA/ Hz MW GW V dB
INPUT NOISE DENSITY
in
0.7
INPUT RESISTANCE Differential Mode Common Mode INPUT VOLTAGE RANGE COMMON-MODE REJECTION RATIO POWER SUPPLY REJECTION RATIO LARGE-SIGNAL VOLTAGE GAIN
RIN RINCM IVR CMRR PSRR
1
10
2
20
mV/V
AVO
1000 800 12.0 10.0 1.7 5
1800 1500 13.8 11.5 2.8 8 70 90 4 140
700 600 11.5 10.0 1.7 5
1500 1500 13.5 11.5 2.8 8 70 100 4 170
V/mV V/mV V V V/ms MHz W mW mV
OUTPUT VOLTAGE SWING SLEW RATE GAIN BANDWIDTH PROD. OPEN-LOOP OUTPUT RESISTANCE POWER CONSUMPTION OFFSET ADJUSTMENT RANGE
VO SR GBW RO Pd
Note 4 VO = 0, IO = 0 Each Amplifier Rp = 10 kW
NOTES 1 Input offset voltage measurements are performed by automated test equipment approximately 0.5 seconds after application of power. E Grade specifications are guaranteed fully warmed up. 2 Long term input offset voltage stability refers to the average trend line of V OS vs. time over extended periods after the first 30 days of operation. Excluding the initial hour of operation, changes in V OS during the first 30 days are typically 2.5 mV. Refer to the Typical Performance Curve. 3 Sample tested. 4 Parameter is guaranteed by design. 5 See test circuit and frequency response curve for 0.1 Hz to 10 Hz tester. 6 See test circuit for current noise measurement. 7 Guaranteed by input bias current. Specifications subject to change without notice.
-2-
REV. A
OP227
SPECIFICATIONS
Individual Amplifier Characteristics (V =
S
15 V, -25 C TA +85 C, unless otherwise noted.)
OP227E Typ 40 Max 140 Min OP227G Typ 85 Max 280 Unit mV mV/ C nA nA V dB mV/V V/mV V
Parameter INPUT OFFSET VOLTAGE AVERAGE INPUT OFFSET DRIFT INPUT OFFSET CURRENT INPUT BIAS CURRENT INPUT VOLTAGE RANGE COMMON-MODE REJECTION RATIO POWER SUPPLY REJECTION RATIO LARGE-SIGNAL VOLTAGE GAIN OUTPUT VOLTAGE SWING
Symbol VOS TCVOS TCVOSn IOS IB IVR CMRR PSRR
Conditions Note 1
Min
Note 2
0.5 10 14 10 11.8 124
1.0 50 60 10 96
0.5 20 25 11.8 118
1.8 135 150
VCM = 10 V VS = 4.5 V to 18 V RL 2 kW, VO = 10 V RL
S
110
2
15
2
32
AVO VO
750 11.7
A
1500 13.6
450 11.0
1000 13.3
2 kW
Matching Characteristics (V = 15 V, T = 25 C, unless otherwise noted.)
Parameter INPUT OFFSET VOLTAGE MATCH AVERAGE NONINVERTING CURRENT NONINVERTING OFFSET CURRENT INVERTING OFFSET CURRENT COMMON-MODE REJECTION RATIO MATCH POWER SUPPLY REJECTION RATIO MATCH CHANNEL SEPARATION Symbol VOS Conditions Min OP227E Typ 25 10 Max 80 40 Min OP227G Typ 55 15 Max 300 90 Unit mV Bias nA
IB +
IB + =
I B + A +I B + B 2
IOS+ IOSCMRR
IOS+ = IB+A-IB+B IOS- = IB-A-IB-B VCM = 11 V VS = 4 V to 18 V Note 1 126 110
12 12 123
60 60 97
20 20 117
130 130
nA nA
dB
PSRR
2 154
10 126
2 154
20
mV/V dB
CS
NOTES 1 Input Offset Voltage measurements are performed by automated equipment approximately 0.5 seconds after application of power. 2 The TCVOS performance is within the specifications unnulled or when nulled with R P = 8 kW to 20 kW, optimum performance is obtained with R P = 8 kW. 3 Sample tested. Specifications subject to change without notice.
REV. A
-3-
OP227-SPECIFICATIONS
Matching Characteristics (V =
S
15 V, TA = -25 C to +85 C, unless otherwise noted.)
Min OP227E Typ 40 Max 140 1.0 60 Min OP227G Typ 90 0.5 25 Max 400 1.8 170 Unit mV mV/ C nA
Parameter INPUT OFFSET VOLTAGE MATCH INPUT OFFSET TRACKING AVERAGE NONINVERTING BIAS CURRENT AVERAGE DRIFT OF NONINVERTING BIAS CURRENT NONINVERTING OFFSET CURRENT AVERAGE DRIFT OF NONINVERTING OFFSET CURRENT INVERTING OFFSET CURRENT COMMON-MODE REJECTION RATIO MATCH POWER SUPPLY REJECTION RATIO MATCH
NOTES *Sample tested.
Symbol VOS TC VOS IB +
Conditions
Nulled or Unnulled*
0.3 14
IB + =
I B + A +I B + B 2
TCIB+ IOS+ TCIOS+ IOS- CMRR IOS- = IB-A-IB-B VCM = 10 V VS = 4.5 V to 18 V 106 IOS+ = IB+A-IB+B
80 20 130 20 120 90 90 90
180 35 250 35 112 250 250
pA/ C nA
pA/ C nA
dB mV/V
PSRR
2
15
3
32
Specifications subject to change without notice.
-4-
REV. A
OP227
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 V Input Voltage1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 V Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Differential Input Voltage2 . . . . . . . . . . . . . . . . . . . . . . . 0.7 V Differential Input Current2 . . . . . . . . . . . . . . . . . . . . . 25 mA Storage Temperature Range . . . . . . . . . . . . . -65C to +150C Operating Temperature Range OP227E, OP227G . . . . . . . . . . . . . . . . . . . . -25C to +85C Lead Temperature (Soldering 60 sec) . . . . . . . . . . . . . . 300C
NOTES 1 For supply voltages less than 22 V, the absolute maximum input voltage is equal to the supply voltage. 2 The OP227 inputs are protected by back-to-back diodes. Current limiting resistors are not used in order to achieve low noise. If differential input voltage exceeds 0.7 V, the input current should be limited to 25 mA. 3 JA is specified for worst-case mounting conditions, i.e., JA is specified for device in socket for CERDIP package.
ABSOLUTE MAXIMUM RATINGS
THERMAL CHARACTERISTICS Thermal Resistance
14-Lead CERDIP 3 JA = 106C/W JC = 16C/W
ORDERING GUIDE
TA = 25 C VOS MAX ( V) 80 180
Hermetic DIP 14-Lead OP227EY OP227GY
Operating Temperature Range IND IND
For military processed devices, please refer to the Standard Microcircuit Drawing (SMD) available at www.dscc.dla.mil/programs/milspec/default.asp. SMD Part Number 5962-8688701CA* ADI Equivalent OP227AYMDA
*Not recommended for new design, obsolete April 2002.
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the OP227 features propriety ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefor, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
REV. A
-5-
OP227-Typical Performance Characteristics
0.1 F 100k 10
VOLTAGE NOISE - nV
BACK-TO-BACK 47 F
1 SEC / DIV 120 2k 5F OP12 100k 0.1 F 24.3k 110k 2.35 F SCOPE X1 RIN = 1M
100
D.U.T.
4.3k
23.5 F
80 40 0 -40 -80 -120
90
VOLTAGE GAIN = 50,000
10 0%
BACK-TO-BACK 10 F
BACK-TO-BACK 4.7 F
0.1Hz TO 10Hz PEAK-TO-PEAK NOISE
TPC 1. Voltage Noise Test Circuit (0.1 Hz to 10 Hz p-p)
TPC 2. Low Frequency Noise (Observation Must Be Limited to 10 Seconds to Ensure 0.1 Hz Cutoff)
10
741
VOLTAGE NOISE DENSITY - nV/ Hz
5 4 3 l/f CORNER = 2.7Hz
rms VOLTAGE NOISE - V
VOLTAGE NOISE - nV/ Hz
10 9 8 7 6
100
TA = 25 C VS = 15V
TA = 25 C VS = 15V 1
10
2
l/f CORNER LOW NOISE AUDIO OP AMP l/f CORNER 2.7 Hz l/f CORNER OP227
0.1
1
1
10 100 FREQUENCY - Hz
1k
10
1
INSTRUMENTATION RANGE, TO DC 10
AUDIO RANGE TO 20 kHz 100
1k
0.01 100
FREQUENCY - Hz
1k 10k BANDWIDTH - Hz
100k
TPC 3. Voltage Noise Density vs. Frequency
TPC 4. Comparison of Op Amp Voltage Noise Spectra
TPC 5. Input Wideband Noise vs. Bandwidth (0.1 Hz to Frequency Indicated)
100
TOTAL NOISE - nV/ Hz
RS = 2R1
4 AT 10Hz
10
3 AT 1kHz
CURRENT NOISE - pA/ Hz
R2
VOLTAGE NOISE DENSITY - nV/ Hz
TA = 25 C VS = 15V
5 R1 VS = 15V
10.0
1.0
AT 10Hz AT 1kHZ RESISTOR NOISE ONLY 1 100 1k SOURCE RESISTANCE - 10k
2
l/f CORNER = 140Hz 0.1 10
1 -50
-25
0
25
50
75
100
125
TEMPERATURE - C
100 1k FREQUENCY - Hz
10k
TPC 6. Total Noise vs. Source Resistance
TPC 7. Voltage Noise Density vs. Temperature
TPC 8. Current Noise Density vs. Frequency
-6-
REV. A
OP227
10 9
120 100 80 OFFSET VOLTAGE DRIFT WITH TIME - V
5 4 3 2 0.2 V/MO. 1 0 -1 -2 -3 -4 -5 0 1 2 3 45678 TIME - MONTHS 9 10 11 12 0.2 V/MO. 0.2 V/MO.
SUPPLY CURRENT - mA (BOTH AMPLIFIERS ON)
8 TA = +25 C 7 6 5 4 3 2 5 10 15 20 25 30 35 40 TOTAL SUPPLY VOLTAGE - V 45 TA = -55 C TA = +125 C
OFFSET VOLTAGE - V
60 40 20 0 -20 -40 -60 -80
-100 -75-55-35-15 5 25 45 65 85 105125145165 TEMPERATURE - C
TPC 9. Supply Current vs. Supply Voltage
TPC 10. Offset Voltage Drift of Representative Units
TPC 11. Offset Voltage Stability with Time
CHANGE IN INPUT OFFSET VOLTAGE - V
30
50 VS = 15V INPUT BIAS CURRENT - nA 40 VS = 15V
ABSOLUTE CHANGE IN INPUT OFFSET VOLTAGE - V
TA = 25 C VS = 15V 10 OP227G
25 20 TA = 25 C TA = 70 C
30
15
5
20
10
5
THERMAL SHOCK RESPONSE BAND DEVICE IMMERSED IN 70 C OIL BATH 0 20 40 60 TIME - Sec 80 100
10
0
0
2 3 4 1 TIME AFTER POWER ON - MINUTES
5
0 -20
0
-50 -25
0 25 50 75 100 125 150 TEMPERATURE - C
TPC 12. Warm-Up Drift
TPC 13. Offset Voltage Change Due to Thermal Shock
TPC 14. Input Bias Current vs. Temperature
SLEW RATE - V/ s PHASE MARGIN - DEG
50 VS = INPUT OFFSET CURRENT - nA 40 15V
OPEN-LOOP GAIN - dB
130 110 90 70 50 30 10
70 M 60 GBW 50 4 VS = 15V
10
9
30
8
20
3 SLEW 2 0 25 50 75 -75 -50 -25 TEMERATURE - C
7
10
0 0 25 50 75 -75 -50 -25 TEMPERATURE - C
-10
100 125
1
10
100
1k 10k 100k 1M 10M 100M FREQUENCY - Hz
8 100 125
TPC 15. Input Offset Current vs. Temperature
TPC 16. Open-Loop Gain vs. Frequency
TPC 17. Slew Rate, Gain Bandwidth Product, Phase Margin vs. Temperature
REV. A
-7-
GAINBANDWIDTH PRODUCT - MHz
OP227
25 20 15 GAIN TA = 25 C VS = 15V 80 100
2.5 RL = 2k
OPEN-LOOP GAIN - V/ V
18 16 14
2.0 OUTPUT SWING - V TA = 25 C 1.5 RL = 1k
120 140 160 180 200 220 100M
PHASE SHIFT - DEG
12 10 8 6 4 2
POSITIVE SWING NEGATIVE SWING
GAIN - dB
10 5 0 -5 10 1M
PHASE MARGIN = 70
1.0
0.5
0.0
10M FREQUENCY - Hz
0
10 20 30 40 TOTAL SUPPLY VOLTAGE - V
50
0 TS = 25 C VS = 15V -2 1k 100 LOAD RESISTANCE -
10k
TPC 18. Gain, Phase Shift vs. Frequency
TPC 19. Open-Loop Gain vs. Supply Voltage
TPC 20. Output Swing vs. Resistive Load
28 PEAK-TO-PEAK OUTPUT VOLTAGE - V 24 20 16 12 8 4 0 1k
SHORT-CIRCUIT CURRENT - mA
TA = 25 C VS = 15V
100
60 TA = VS = 50 lSC(-) 25 15V
80 PERCENT OVERSHOOT
60
40
40
VS = 615V VIN = 100mV AV = +1
30 lSC(+) 20
20
10k
100k 1M FREQUENCY - Hz
10M
0
0
500 1000 1500 2000 CAPACITIVE LOAD - pF
2500
20
0
2 3 4 1 TIME FROM OUTPUT SHORTED TO GROUND - MINUTES
5
TPC 21. Maximum Undistorted Output vs. Frequency
TPC 22. Small-Signal Overshoot vs. Capacitive Load
TPC 23. Short-Circuit Current vs. Time
140
20mV +50mV
100 90
500ns +5V
100 90
2V
2s
120
0V
0V
CMMR - dB
10 0%
100
10 0%
-50mV
80
-5V
AVCL = +1, CL= 15pF VS = 15V TA = 25 C
AVCL = +1 VS = 15V TA = 25 C
60 1k
10k
100k 1M FREQUENCY - Hz
10M
TPC 24. Small-Signal Transient Response
TPC 25. Large-Signal Transient Response
TPC 26. Matching Characteristic CMRR Match vs. Frequency
-8-
REV. A
OP227
16 12
COMMON-MODE RANGE - V
2.4 OPEN-LOOP VOLTAGE GAIN - V/ V 2.2 2.0 1.8 1.6 1.4
PSRR AND
140 TA = 25 C VS = 15V
PSSR - dB
8 4 0 -4 -8
TA = +25 C
TA = -55 C
TA = +125 C
120 100 PSRR (+) PSRR (-) 60 40 20 1
PSRR (-)
PSRR (+)
80
TA = -55 C TA = +25 C
1.2 1.0 0.8 0.6 0.4 100 1k 10k LOAD RESISTANCE - 100k
TA = +125 C
-12 -16 0 5 10 15 SUPPLY VOLTAGE - V 20
10
100 1k 10k FREQUENCY - Hz
100k
1M
TPC 27. Common-Mode Input Range vs. Supply Voltage
TPC 28. Open-Loop Voltage Gain vs. Load Resistance
TPC 29. PSRR and PSRR vs. Frequency
100 80 OFFSET VOLTAGE MATCH - V 60 40 20 0 -20 -40 -60 -80
nA
40
50
NONINVERTING BIAS CURRENT -
30
nA OFFSET CURRENT -
5 25 45 65 85 105 125 TEMPERATURE - C
40
20
30
10
20
-100 -120 -75 -55-35-15 5 25 45 65 85 105125145165 TEMPERATURE - C
0 -55 -35 -15
10 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE - C
TPC 30. Matching Characteristic: Drift of Offset Voltage Match of Representative Units
TPC 31. Matching Characteristic: Average Noninverting Bias Current vs. Temperature
TPC 32. Matching Characteristic: Average Offset Current vs. Temperature (Inverting or Noninverting)
125
180
CHANNEL SEPARATION - dB
120 CMRR - dB
140
120
115
100
110
80
105 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE - C
60 100
1k
10k 100k FREQUENCY - Hz
1M
10M
TPC 33. Matching Characteristic: CMRR Match vs. Temperature
TPC 34. Channel Separation vs. Frequency
REV. A
-9-
OP227
BASIC CONNECTIONS
V+(A) 10k 2 1 14
A noise-voltage-density test is recommended when measuring noise on a large number of units. A 10 Hz noise-voltagedensity measurement will correlate well with a 0.1 Hz to 10 Hz peak-to-peak noise reading, since both results are determined by the white noise and the location of the 1/f corner frequency.
Instrumentation Amplifier Applications of the OP227
(-) INPUTS (+)
3 A 4 12 V-(A) 13 OUT (A)
The excellent input characteristics of the OP227 make it ideal for use in instrumentation amplifier configurations where low level differential signals are to be amplified. The low noise, low input offsets, low drift, and high gain, combined with excellent CMR provide the characteristics needed for high performance instrumentation amplifiers. In addition, CMR versus frequency is very good due to the wide gain bandwidth of these op amps. The circuit of Figure 2 is recommended for applications where the common-mode input range is relatively low and differential gain will be in the range of 10 to 1000. This two op amp instrumentation amplifier features independent adjustment of common-mode rejection and differential gain. Input impedance is very high since both inputs are applied to non-inverting op amp inputs.
R0
OP227
5 (+) INPUTS (-) 10 11 B 6 OUT (B) V-(B)
9
8 10k
7
R1
R2
V+(A)
A1 VCM - 1/2Vd R3
V1
R4
Figure 1. Offset Nulling Circuit
VCM + 1/2Vd
A2 VO = R4 R3 + [1+ 1 (R2 + R3 ) + R2R0R3 ] V 2 R1 R4 R4
VO
APPLICATIONS INFORMATION Noise Measurements
d + R3
(R3 - R2 ) V R4 R1
CM
To measure the 80 nV peak-to-peak noise specification of the OP227 in the 0.1 Hz to 10 Hz range, the following precautions must be observed: * The device must be warmed up for at least five minutes. As shown in the warm-up drift curve, the offset voltage typically changes 4 mV due to increasing chip temperature after power-up. In the 10-second measurement interval, these temperatureinduced effects can exceed tens-of-nanovolts. For similar reasons, the device must be well shielded from air currents. Shielding minimizes thermocouple effects. Sudden motion in the vicinity of the device can also "feedthrough" to increase the observed noise. The test time to measure 0.1 Hz to 10 Hz noise should not exceed 10-seconds. As shown in the noise-tester frequencyresponse curve, the 0.1 Hz corner is defined by only one zero to eliminate noise contributions from the frequency band below 0.1 Hz.
Figure 2. Two Op Amp Instrumentation Amplifier Configuration
The output voltage VO, assuming ideal op amps, is given in Figure 2. the input voltages are represented as a common-mode input, VCM, plus a differential input, Vd. The ratio R3/R4 is made equal to the ratio R2/R1 to reject the common mode input VCM. The differential signal VO is then amplified according to:
E VO = R 4 A1 + R3 + R2 + R3 V d , where R3 = R2 R3 E R4 RO R 4 R1
Note that gain can be independently varied by adjusting RO. From considerations of dynamic range, resistor tempco matching, and matching of amplifier response, it is generally best to make R1, R2, R3, and R4 approximately equal. Designing R1, R2, R3, and R4 as RN allows the output equation to be further simplified:
V
O
E R = 2A 1 + N Vd , where RN = R1 = R2 = R3 = R4 R E O
-10-
REV. A
OP227
Dynamic range is limited by A1 as well as A2. The output of A1 is:
E R V1 = - A1 + N V d + 2 V CM RO E
If the instrumentation amplifier was designed for a gain of 10 and maximum Vd of 1 V, then RN/RO would need to be four and VO would be a maximum of 10 V. Amplifier A1 would have a maximum output of 5 V plus 2 VCM, thus a limit of 10 V on the output of A1 would imply a limit of 2.5 V on VCM. A nominal value of 10 kW for RN is suitable for most applications. A range of 20 W to 2.5 kW for RO will then provide a gain range of 10 to 1000. The current through RO is Vd/RO, so the amplifiers must supply 10 mV/20 W (or 0.5 mA) when the gain is at the maximum value of 1000 and Vd is at 10 mV. Rejecting common-mode inputs is important in accurately amplifying low level differential signals. Two factors determine the CMR in this instrumentation amplifier configuration (assuming infinite gain): CMR of the op amps Matching of the resistor network ratios (R3/R4 = R2/R1) In this instrumentation amplifier configuration error due to CMR effect is directly proportional to the CMR match of the op amps. For the OP227, this DCMR is a minimum of 97 dB for the "G" and 110 dB for the "E" grades. A DCMR value of 100 dB and a common-mode input range of 2.5 V indicates a peak inputreferred error of only 25 mV. Resistor matching is the other factor affecting CMR. Defining Ad as the differential gain of the instrumentation amplifier and assuming that R1, R2, R3, and R4 are approximately equal (RN will be the nominal value), then CMR for this instrumentation amplifier configuration will be approximately Ad divided by 4 R/RN. CMR at differential gain of 100 would be 88 dB with resistor matching of 0.01%. Trimming R1 to make the ratio R3/R4 equal to R2/R1 will raise the CMR until limited by linearity and resistor stability considerations. The high open-loop gain of the OP227 is very important to achieving high accuracy in the two op amp instrumentation amplifier configuration. Gain error can be approximated by:
For Ad/A01 < 1, this simplifies to (2Ad/A01) 3 VCM. If the op amp gain is 700 V/mV, VCM is 2.5 V, and Ad is set to 700, then the error at the output due to this effect will be approximately 5 mV. A compete instrumentation amplifier designed for a gain of 100 is shown in Figure 3. It has provision for trimming of input offset voltage, CMR, and gain. Performance is excellent due to the high gain, high CMR, and low noise of the individual amplifiers combined with the tight matching characteristics of the OP227 dual.
OFFSET V+ 10k 2 1 14 ADJUST
CMR 10k 0.1% 50
9.95k 3 13 VCM - 1/2Vd 2.5k GAIN 4 12 V-
OP227
7 191 10 6 VCM - 1/2Vd 11 5 V- VO = 100Vd V+
10k , 0.1% 10k , 0.1%
Figure 3. Two Op Amp Instrumentation Amplifier Using OP227 Dual
Gain Error
Ad 1 , <1 Ad 2 AO1 AO1 1+ AO 2
A three op amp instrumentation amplifier configuration using the OP227 and OP27 is recommended for applications requiring high accuracy over a wide gain range. This circuit provides excellent CMR over a wide frequency range. As with the two op amp instrumentation amplifier circuits, the tight matching of the two op amps within the OP227 package provides a real boost in performance. Also, the low noise, low offset, and high gain of the individual op amps minimize errors. A simplified schematic is shown in Figure 4. The input stage (A1 and A2) serves to amplify the differential input Vd without amplifying the common-mode voltage VCM. The output stage then rejects the common-mode input. With ideal op amps and no resistor matching errors, the outputs of each amplifier will be: E V V1 = - A1 + 2R1 d + V CM RO 2 E E V V2 = - A1 + 2R1 d + V CM RO 2 E E VO = V2 - V1 = A1 + 2R1 V d RO E -11- VO = Ad V d
where Ad is the instrumentation amplifier differential gain and AO2 is the open loop gain of op amp A2. This analysis assumes equal values of R1, R2, R3, and R4. For example, consider an OP227 with AO2 of 700 V/mV. Id the differential gain Ad were set to 700, then the gain error would be 1/1.001, which is approximately 0.1%. Another effect of finite op amp gain is undesired feedthrough of common-mode input. Defining AO1 as the open-loop gain of op amp A1, then the common-mode error (CME) at the output due to this effect would be approximately:
CME 2 Ad , 1 V CM Ad AO1 1+ AO 2
REV. A
OP227
The differential gain Ad is 1 + 2R1/R0 and the common-mode input VCM is rejected. While output error due to input offsets and noise are easily determined, the effects of finite gain and common-mode rejection are more subtle. CMR of the complete instrumentation amplifier is directly proportioned to the match in CMR of the input op amps. This match varies from 97 dB to 110 dB minimum for the OP227. Using 100 dB, then the output response to a common-mode input VCM would be: CMRR AO DAO
2
If AO/AO were 6% and AO were 600,000, then the CMRR due to finite gain of the input op amps would be approximately 140 dB.
R1
1/2
VO = (1 + 2R1 ) Vd
R0
[V ]
O
OP227
A1 VCM - 1/2Vd R2 V1 R2
CM
= Ad V CM 10-5
CMRR of the instrumentation amplifier, which is defined as 20 log10Ad/ACM, is simply equal to the CMRR of the OP227. While this CMRR is already high, overall CMRR of the complete amplifier can be raised by trimming the output stage resistor network. Finite gain of the input op amps causes a scale factor error and a small degradation in CMR. Designating the open-loop gain of op amp A1 as AO1, and op amp A2 as AO2, then the following equation approximates output:
E 2R1 E 1 1 V - AA V + A Add R0 E A A CM R1 E 1 1 E O1 O2 + 1+ A R0 E A A O1 O2 1
OP27 R0 R1 A3 VO
1/2
OP227
A2 VCM + 1/2Vd V2 R2 R2
V
Figure 4. Three Op Amp Instrumentation Amplifier Using OP227 and OP27
O
This can be simplified by defining AO as the nominal open-loop gain and A0 as the differential open-loop gain. Then:
VO
E 2R1 DAO V 1 A Ad V d + R0 CM 2 AO 1 + R1 1 E R0 AO
The unity-gain output stage contributes negligible error to the overall amplifier. However, matching of the four resistor R2 network is critical to achieving high CMR. Consider a worstcase situation where each R2 resistor had an error of R2. If the resistor ratio is high on one side and low on the other, then the common-mode gain will be 2 R2/2 R2. Since the output stage gain is unity, CMRR will then be R2/2 R2. It is common practice to maximize overall CMRR for the total instrumentation amplifier circuit.
The high open-loop gain of each amplifier within the OP227 (700,000 minimum at 25C in RL 2 kW) assures good gain accuracy even at high values of Ad. The effect of finite openloop gain on CMR can be approximated by:
-12-
REV. A
OP227
High Speed Precision Rectifier
The low offsets and excellent load driving capability of the OP27 are key advantages in this precision rectifier circuit. The summing impedances can be as low as 1 kW which helps to reduce the effects of stray capacitance. For positive inputs, D2 conducts and D1 is biased OFF. Amplifiers A1 and A2 act as a follower with output-to-output feedback and the R1 resistors are not critical. For negative inputs, D1 conducts and D2 is biased OFF. A1 acts as a follower and A2 serves as a precision inverter. In this mode, matching of the two R1 resistors is critical to gain accuracy.
Typical component values are 30 pF for C1 and 2 kW for R3. The drop across D1 must be less than the drop across the FET diode D2. A 1N914 for D1 and a 2N4393 for the JFET were used successfully. The circuit provides full-wave rectification for inputs of up to 10 V and up to 20 kHz in frequency. To assure frequency stability, be sure to decouple the power supply inputs and minimize any capactive loading. An OP227, which is two OP27 amplifiers in a single package, can be used to improve packaging density.
R1* 1k C1 30pF D1 1N914
R2* 1k
* MATCHED
A1 V1 A1, A2: OP27 2N4393
D2
A2
VO
R3 2k
Figure 5. High Speed Precision Rectifier
REV. A
-13-
OP227
OUTLINE DIMENSIONS 14-Lead Ceramic Dip - Glass Hermetic Seal [CERDIP] (Q-14)
Dimensions shown in inches and (millimeters)
0.005 (0.13) MIN
14
0.098 (2.49) MAX
8 7
PIN 1
1
0.310 (7.87) 0.220 (5.59) 0.320 (8.13) 0.290 (7.37) 0.060 (1.52) 0.015 (0.38)
0.100 (2.54) BSC 0.785 (19.94) MAX 0.200 (5.08) MAX 0.200 (5.08) 0.125 (3.18) 0.023 (0.58) 0.014 (0.36)
0.150 (3.81) MIN 0.070 (1.78) SEATING 15 PLANE 0 0.030 (0.76)
0.015 (0.38) 0.008 (0.20)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETERS DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
-14-
REV. A
OP227 Revision History
Location 10/02--Data Sheet changed from REV. 0 to REV. A. Page
Edits to GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 OP227A and OP227F deleted from Individual Amplifier Characteristics section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 OP227A and OP227F deleted from Matching Characteristics section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Edits to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Edits to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
REV. A
-15-
-16-
C02685-0-10/02(A)
PRINTED IN U.S.A.

▲Up To Search▲

Price & Availability of OP227AYMDA

	To Download OP227AYMDA Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .