removing the offset voltage of the op-amp output

[kasser]

I used an operation amplifier for amplifing a low dc signal (about 200uv) from output of thermocoupler ,but I observed a offset voltage one the amplifier output without connecting the input dc signal , after reseach I knew there is offset voltage at the amplifier's output, it changes when ambient temperature changes, Ther are methodes to eliminate it using a variable resistor, but when ambient temperature changes you have to re-balance the variable resistor. Is ther any auto compensation.

thanks in advance.

 

[ericgibbs]

I used an operation amplifier for amplifing a low dc signal (about 200uv) from output of thermocoupler ,but I observed a offset voltage one the amplifier output without connecting the input dc signal , after reseach I knew there is offset voltage at the amplifier's output, it changes when ambient temperature changes, Ther are methodes to eliminate it using a variable resistor, but when ambient temperature changes you have to re-balance the variable resistor. Is ther any auto compensation.

thanks in advance.

hi,
What type of OPA are you using.?

 

[kasser]

op-amp is ua741.

 

[ericgibbs]

op-amp is ua741.

hi kasser,
Thats about the worst specification device I would consider using for very low drift.!

What other OPA's have you got access to.?


EDIT: look at this drawing for Offset Adjustment.