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low noise, high gain, low frequency amplifier

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New Member
I am considering building an amplifier similar to the one shown at: http://www.cn.stir.ac.uk/eegviewer//preamp

This schematic is entitled "Preamp, anti-alias filter and isolation circuit". Right now I am just trying to understand the overall block functionality. I am guessing that the amplifier/filter begins at AMP01's inputs and ends at OP07's outputs and that the rest is isolation and interfacing. Is this correct?

Also, newer/better ICs are no doubt available as an AMP01 substitute. Any recommendations?



Well-Known Member
As far as I can see, the AMP01 and the OP07 provide AC gain. The first NE5532 is a simple low pass filter with a little bit of gain. The second NE5532 drives the optoisolator. I'm not familiar with this configuration, but will guess that the first optoisolator is configured with the amp to linearize the frequency response through the second optoisolator. The final TL071 amp is simply a unity gain buffer amp to drive the output with a low source impedance. Isolation is achieved before the TL071 using the optoisolator and using independent power supply and ground on either side.

Nigel Goodwin

Super Moderator
Most Helpful Member
The circuit round the second NE5532 is quite interesting, I suspect the first opto-isolator is intended to give a nice fast square pulse from the rather random input waveform.

I would tend to build it and test it, but I suspect someone will simulate it a LOT faster? :D
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