# What could be maximum gain of opamp to be set for DC application ???

#### BobTPH

Joined Jun 5, 2013
6,070
Long before you get to the open loop gain, the input offset will send the output to one rail ot the other.

Bob

#### atferrari

Joined Jan 6, 2004
4,671
You should tell the input level and the intended output.

#### MrChips

Joined Oct 2, 2009
27,669
Open loop gain typically 100,000.

#### mishra87

Joined Jan 17, 2016
974

I still did not understand ???

My question was can I set the close loop 100 for this opamp.

Suppose I have 30mV dc signal so can I amplify with gain of 100. So that the signal would be 3V.

Current = 3A
Rshunt = 10mOhm

Thanks.

#### Alec_t

Joined Sep 17, 2013
13,224
My question was can I set the close loop 100 for this opamp.
That wasn't your original question, but yes, you can have a closed loop gain of 100.

#### mishra87

Joined Jan 17, 2016
974
That wasn't your original question, but yes, you can have a closed loop gain of 100.
Thanks !!

Now I again ask to you .
How did you say that gain Could be 100.

Means what all parameters need to be taken care while adjusting the opamp gain.

I already stated my application for 3A dc current measurement.

Thanks.

#### BobTPH

Joined Jun 5, 2013
6,070
Check the input offset of your opamp and multiply it by 100. This will tell you the error in your output. For example, if the input offset is 2mV, the output error will be 200mV.

For amplifying mV level signals, an instrumentation amplifier is often required.
B

#### atferrari

Joined Jan 6, 2004
4,671
I already stated my application for 3A dc current measurement.
You did?

#### Alec_t

Joined Sep 17, 2013
13,224
If you did as Bob indicated in post #10 you would have spotted that the datasheet says the specified input offset voltage can be anything between -4.5mV and +4.5mV. If your signal input is only 30mV, that implies a possible error of ± 100 * 4.5/30 = 15%. If you are aiming for better accuracy you would have to either find a way of compensating for the offset, choose a different opamp with smaller offset, or use a dedicated instrumentation amplifier.

#### MrChips

Joined Oct 2, 2009
27,669
Gain of 100 is a walk in the park. If you encounter DC offset there are ways to reduce it.