OPA197 Datasheet, PDF (24/41 Pages) Texas Instruments – Operational Amplifiers

OPA197, OPA2197, OPA4197
SBOS737 – JANUARY 2016
www.ti.com
7.3.6 Common-Mode Voltage Range
The OPAx197 is a 36-V, true rail-to-rail input operational amplifier with an input common-mode range that
extends 100 mV beyond either supply rail. This wide range is achieved with paralleled complementary N-channel
and P-channel differential input pairs, as shown in Figure 50. The N-channel pair is active for input voltages
close to the positive rail, typically (V+) – 3 V to 100 mV above the positive supply. The P-channel pair is active
for inputs from 100 mV below the negative supply to approximately (V+) – 1.5 V. There is a small transition
region, typically (V+) –3 V to (V+) – 1.5 V in which both input pairs are on. This transition region can vary
modestly with process variation, and within this region PSRR, CMRR, offset voltage, offset drift, noise and THD
performance may be degraded compared to operation outside this region.
V+
IS1
±IN
PCH1
+IN
PCH2
NCH3
NCH4
FUSE BANK
TRIM
TRIM
V±
Figure 50. Rail-to-Rail Input Stage
To achieve the best performance for two-stage rail-to-rail input amplifiers, avoid the transition region when
possible. The OPAx197 uses a precision trim for both the N-channel and P-channel regions. This technique
enables significantly lower levels of offset than previous-generation devices, causing variance in the transition
region of the input stages to appear exaggerated relative to offset over the full common-mode voltage range, as
shown in Figure 51.
P-Channel
Region
Transition
Region
N-Channel
Region
P-Channel Transition
Region
Region
N-Channel
Region
200
200
100
100
0
0
±100
±200
OPAx197
Input Offset Voltage vs Vcm
±300
±15.0 ±14.0
« 11.0 12.0 13.0
Common-Mode Voltage (V)
14.0 15.0
±100
±200
Input Offset Voltage vs Vcm
without a precision trimmed Input
±300
±15.0 ±14.0 « 11.0 12.0 13.0
Common-Mode Voltage (V)
Figure 51. Common-Mode Transition vs Standard Rail-to-Rail Amplifiers
14.0 15.0
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