Dual, Low Noise, Low Offset
Instrumentation Operational Amplifier
a
OP227
FEATURES
PIN CONNECTIONS
Excellent Individual Amplifier Parameters
Low VOS, 80 V Max
1
2
3
4
5
6
7
14
13
12
11
10
9
NULL (A)
NULL (A)
V+ (A)
Offset Voltage Match, 80 V Max
Offset Voltage Match vs. Temperature, 1 V/؇C Max
Stable VOS vs. Time, 1 V/MO Max
Low Voltage Noise, 3.9 nV/÷Hz Max
Fast, 2.8 V/s Typ
OUT (A)
V– (A)
–IN (A)
+IN (A)
V– (B)
A
+IN (B)
–IN (B)
NULL (B)
NULL (B)
B
OUT (B)
High Gain, 1.8 Million Typ
High Channel Separation, 154 dB Typ
8
V+ (B)
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
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.
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.
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 param-
eters 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.
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
SIMPLIFIED SCHEMATIC
V+
C2
R3
R1
R4
R2
Q6
Q3
Q22
NULL
Q46
Q45
C1
R9
R12
Q21
R23
R24
*
*
Q20 Q19
Q23
Q24
OUTPUT
NON
INVERTING
INPUT (+)
Q1A Q1B Q2B Q2A
C3
INVERTING
INPUT (–)
R11 C4
R5
Q11
Q12
Q26
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, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 2002