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Old 27th Jun 2017, 10:19 pm   #214
mark_in_manc
Octode
 
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
Default Re: 807 (maybe) amplifier build. Now EL34

I could sketch a pole-zero plot for something simple (2nd order lo-pass or something) and use it to sketch the Bode plot (mag and phase) for the transfer function through it. But now suppose such a network, like this amplifier we're meant to be discussing in this thread (sorry D.A.!) had a feedback path from its output back to its input, with some more jw's in it. We could make an easy (or perhaps better to say 'tractable'!) example of stuff in this path by making it, i don't know, a 2nd order bandpass with magic (pure multiplication) gain of G, say. With the loop broken, that branch doesn't do anything, but with it closed, all that mag and pha complication 'does things'. Supposing the loop re-connects with itself at point A at the overall input, would I break it there and then work out the transfer function from A back round to A (if you see what I mean)? And how do I write down the overall transfer function Vo/Vi when the loop is closed?

Sorry to be dense, but I'm stuck on this. I used to do a lot of this, but (as you can see) never with feedback!
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