RHF330 Datasheet, PDF (18/22 Pages) STMicroelectronics – Rad-hard 1 GHz low noise operational amplifier

Bias of an inverting amplifier
7
Bias of an inverting amplifier
RHF330
A resistance is necessary to achieve good input biasing, such as resistance R shown in
Figure 32.
The value of this resistance is calculated from the negative and positive input bias current.
The aim is to compensate for the offset bias current, which can affect the input offset voltage
and the output DC component. Assuming I_ib-, I_ib+, R_in, R_fb and a zero volt output, the
resistance R is:
R = -^R----ⁱ-ⁿ-----^×-----^R-----^f--^b-
R_in + R_fb
Figure 32. Compensation of the input bias current
R_fb
I-
ib
R
in
_
V+
CC
+
I_ib +
R
V_CC ^-
Output
Load
AM00839
18/22
Doc ID 15576 Rev 3