Hello,
Could anyone tell me what are the restrictions when calculating a typical instrumentation amplifier (3 OPAMP's) cause I've have one which auto-oscilates and I don't understand how to avoid it.
I've realized that the values of the resistances change the amount of oscilations, but I want to obtain a gain at least 50 times V2-V1.

Any tutorial or link about it would help me, Thank you.

A. L. A.

 

Originally posted by ALA@Jun 4 2005, 10:57 AM
Hello,
Could anyone tell me what are the restrictions when calculating a typical instrumentation amplifier (3 OPAMP's) cause I've have one which auto-oscilates and I don't understand how to avoid it.
I've realized that the values of the resistances change the amount of oscilations, but I want to obtain a gain at least 50 times V2-V1.

Any tutorial or link about it would help me, Thank you.

A. L. A.

[post=8206]Quoted post[/post]​

Ordinarily an instrumention amplifier is stable. Is it possible for you to provide a schematic of the circuit hookup?

For any amplifier to oscillate requires the existence of very specific feedback conditions.

Hopefully one of our members can spot something by examining your schematic.

hgmjr

 

hi,

yes it would be best if you can show your schem. however am just curious, is your feedback resistance beyond 500k? if it is then that is your probable cause of instability.

 

Instrumentation Amplifier

 

Hi,

I've have one which auto-oscilates and I don't understand how to avoid it.

Did you decouple the supply properly ?