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Old 19th May 2005, 08:38 PM   #1
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Default Can anyone help with this opamp circuit?

I posted this off to Erno Borbely who was a real gentleman, but hadn't seen it before.

I can't upload it, no scanner, I will try to describe as best I can, perhaps someone could try to draw it?

its the 2nd stage of an IC phonostage.

ne5532 positive input comes from the riaa.

output goes out to the preamp.

in the feedback loop coming off this is the other half of the 5532 with a :

5k series resistor and a 1k to ground, at the positive input,

this is where it gets tricky...

a 5 k feedback resistor and 1k to ground goes to both the negative of the feedback opamp, AND the negative terminal of the original half of the first opamp.

That's as clear as I can make it, any ideas on what the feedback opamps function is, desperate to find out.

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Old 20th May 2005, 02:24 AM   #2
jcx is offline jcx  United States
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at you can download the free Lt SwCAD III spice tool, its easy to draw with, just use any standard op amp to show us the circuit - capture a screen shot with paint, crop and save as .gif (not jpg!)
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Old 20th May 2005, 02:59 AM   #3
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Something like this? I ran a simulation on it, and it shows a gain of 6.
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Old 20th May 2005, 07:45 AM   #4
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spot on xplod....that's it anyone know what the feedback opamp does?

if no-one replies, I shall try a post in the opamp section, or a new one here.

brilliant, thanks guys, IM
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Old 20th May 2005, 10:12 AM   #5
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Funny, this very topic was discussed here yesterday.
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