# amplifier How does this circuit attenuate high frequencies

Posted on Feb 6, 2014

This circuit could be used as a treble control circuit with high frequency gain occuring when R3 is set so a=b (we`ll call this k=0), and high frequency attenuation occuring when R3 is 22kOhms across a and b (k=1). So therefore, depending on R3`s setting, this circuit is either a high pass (k=0) or low pass (k=1) filter. When comparing this circuit to high and low pass filters,

I do not understand what is happening: C2 will always have a lower impedance for high frequencies and so surely adjusting R3 will only alter positive gain for high frequencies. It`s not a duplicate, but you are trying to understand this circuit without having clear what the simgle parts do. Did you understand how the feedback works for an amplifier clabacchio™ May 16 `12 at 9:44 @clabacchio Yes, I think so. I understand that DC feedback is needed to control any fluctuations in voltage between the virtual ground input nodes to the amplifier. It does this by outputing the signal with a DC offset opposite to that at the inputs. Although AC feedback can travel over a capacitor, for any DC signal it acts like an open circuit. user1083734 May 16 `12 at 9:50 I am a beginner but am finding all of the answers I have recieved on electronics. I realise the power of this resourse and certainly do not want to waste anybody`s time user1083734 May 16 `12 at 9:52 It`s not about that: you have to understand that DC feedback and AC feedback are, in principle, feedbacks. From your first comment I see some confusion, and I don`t blame you :) but you should take things a bit more step by step. I`ve also edited my answer to give a bit more general notions, check it. clabacchio™ May 16 `12 at 10:00

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