DC Amplifier Oscillation Issue

Thread Starter

Federov

Joined Sep 14, 2010
26
mik3, I can't thank you enough for all your help. You have confirmed most of my my thoughts so I can relax a little bit =P haha.

I'm a little confused still on the 180 degrees phase shifted output you mentioned. You stated what I thought was happening but thats half the reason I was confused =P. I guess what im asking is what is causing this 180 degree phase shift back to the non-inverting terminal and.. how can this be proven or described?
 
Last edited:

Audioguru

Joined Dec 20, 2007
11,248
The transistor is a common-emitter type so its collector output is 180 degrees from its input from the output of the opamp. So when the transistor feeds its inverted output to the (+) input of the opamp it is negative feedback.
 

Thread Starter

Federov

Joined Sep 14, 2010
26
Ahh yes i forgot all about that quality of the CE amplifier, thank you Audioguru =). Things you forget within a year of learning them.. scary lol. This characteristic is a little harder to see considering all the voltages are DC. Its hard to wrap my head around phase shifting a DC value 180 degrees resulting in negative feedback to the positive terminal.. probably just thinking about it wrong once again.
 
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