Amplify opamp output voltage

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Hmmmm, that seems too good to be true, I'm wondering what the catch is, all the rest are hundreds of dollars and my 45v "high voltage" opamp I use right now costs $11. Would that opamp serve well as a DC offset servo?
 
  • #28
jim hardy
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Hmmmm, that seems too good to be true, I'm wondering what the catch is.
Well their metal cased power boosters are $150
this one is plastic - maybe that's why it's so cheap...
Would that opamp serve well as a DC offset servo?
Well, "DC offset servo" probably is basic vocabulary to folks in your field
but i don't know what you mean by it.
Can you add some detail?

ps again i never used one. LM12CL was my workhorse until they went from $12 to $80-ish.

old jim
 
  • #29
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By DC offset servo I mean an opamp integrator that I use to bias a triode to maintain a DC null at the output of the stage. As in the non inverting input is attached to ground and the inverting input is attached to the output of the stage and I adjust a trimmer so the opamp outputs a proper bias voltage to maintain a DC null at the output of the stage based on its input.
 
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  • #30
jim hardy
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Integrator... max input bias is 200 picoamps 50 typ

if you don't need real long time constant it oughta do fine

200 pa into 1uf is 200 microvolts per second at output,
or 200 microvolts error at input with 1 meg input resistance

that's how i 'rule of thumb' size them up...

sound reasonable?
 
  • #31
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A time constant of around 1hz would work. Thanks jim you're a hero :) Now onto the next issue.
 
  • #32
jim hardy
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By DC offset servo I mean an opamp integrator that I use to bias a triode to maintain a DC null at the output of the stage. As in the non inverting input is attached to ground and the inverting input is attached to the output of the stage and I adjust a trimmer so the opamp outputs a proper bias voltage to maintain a DC null at the output of the stage based on its input.
A question well stated is halfway answered.

Bravo - that was very clear !

thanks, and good luck !
old jim
 
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