How to test the Offset Voltage and Offset Current of a OP?

[ZengLei]

offset current

any idears of how to test them?

and how to eliminate the negative effects of them in our applications ?

Thanks~~~~

 

[subharpe]

op offset voltage offset current

There are many ways. The simplest way is to tie both the inputs to ground and finding the output in open loop condition.This output gives the output offset voltage and that divided by the open loop gain (which is often specified in the datasheets) gives the input offset.

The links might help
**broken link removed**
http://www.ecircuitcenter.com/Circuits/op_voff/op_voff.htm

 

[laktronics]

offset current junction

Hi,
You measure offset voltage by configuring the opamp as a high gain closed loop inverting amplifier with zero input voltage and with relatively low feedback resistor such that the effect of offset current is negligible in the measurement. The voltage offset referred to input is then calculated by dividing the DC voltage appearing at the output of the amplifier by the closed loop gain.

For measuring the offset current, connect a high feed back resistance across the summing junction and output of the amplifier and measure the output DC voltage. The offset current referred to input is then calculated by dividing the output voltage by the feedback resistor value.

The effects of voltage offset is adjusted by using an offset adjust potetiometer connected across the adjustment pins provided by the IC manufacturer for many IC opamps. The effects of current offset is reduced by using minimum required value for the feed back resistor and also by matching the DC resistance levels at both positive and negative inputs of the opamp. You can also inject a small current into the summing junction of the opamp to compensate for the current offset.

Regards,
Laktronics

 

[Asif2008]

how do you measure a voltage offset?

u should ground the both input and check the out put