APPLICATIONS INFORMATION
V+
The OPA131 series op amps are unity-gain stable and
suitable for a wide range of general-purpose applications.
Power-supply pins should be bypassed with 10nF ceramic
capacitors or larger.
OPA131
(Single op amp only)
7
2
3
6
OPA131
5
The OPA131 series op amps are free from unexpected
output phase-reversal common with FET op amps. Many
FET-input op amps exhibit phase-reversal of the output when
the input common-mode voltage range is exceeded. This can
occur in voltage-follower circuits, causing serious problems
in control-loop applications. All circuitry is completely inde-
pendent in dual and quad versions, assuring normal behavior
when one amplifier in a package is overdriven or short-
circuited.
1
4
100kΩ
Trim Range: ±20mV typ
V–
FIGURE 1. OPA131 Offset Voltage Trim Circuit.
INPUT BIAS CURRENT
OFFSET VOLTAGE TRIM
The input bias current is approximately 5pA at room tem-
perature and increases with temperature as shown in the
typical characteristic “Input Bias Current vs Temperature.”
The OPA131 (single op amp version) provides offset volt-
age trim connections on pins 1 and 5. Offset voltage can be
adjusted by connecting a potentiometer as shown in Figure
1. This adjustment should be used only to null the offset of
the op amp, not system offset or offset produced by the
signal source.
Input bias current also varies with common-mode voltage
and power supply voltage. This variation is dependent on the
voltage between the negative power supply and the com-
mon-mode input voltage. The effect is shown in the typical
curve “Input Bias Current vs Common-Mode Voltage.”
OPA131, 2131, 4131
7
SBOS040A
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