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Diff-amp question

S

Samuel Groner

Jan 1, 1970
0
Hi,

I've got a question regarding the basic diff-amp config with one opamp
and four resistors. Does the resistor connected output and "-"-input
load the opamp?

Thanks
Samuel
 
J

John Larkin

Jan 1, 1970
0
Hi,

I've got a question regarding the basic diff-amp config with one opamp
and four resistors. Does the resistor connected output and "-"-input
load the opamp?

Thanks
Samuel


Sure. And it can self-heat and mess up the CMRR.

I've added a follower opamp before the feedback resistor, inside the
loop, to reduce the heating of the first amp, to reduce thermal
offsets and transient hooks.

John
 
I

Ian Bell

Jan 1, 1970
0
Samuel said:
Hi,

I've got a question regarding the basic diff-amp config with one opamp
and four resistors. Does the resistor connected output and "-"-input
load the opamp?

Thanks
Samuel

Yes, because it at least provides bias current for the input and depending
on the configuration (such as a diff amp) it may be a virtual earth. Is
this a problem. usually this resistor value is high enough for it not to
significantly load the output.

ian
 
S

Samuel Groner

Jan 1, 1970
0
Thanks for the answers! Thought that, but nowhere read about it, so was not sure..
Samuel
 
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