APPLICATIONS INFORMATION
V+
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 capaci-
tors or larger.
OPA131
(Single op amp only)
7
2
3
6
OPA131
5
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
independent 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 performance curve “Input Bias Current vs Tempera-
ture.”
The OPA131 (single op amp version) provides offset
voltage 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.”
®
7
OPA131/2131/4131