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wado1942

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Posts posted by wado1942

  1. Well the inverting amp configuration works like a charm so I'm going with that.  My next challenge is adding a -10dB switch.  Any suggestions?  I was thinking a resistor to shunt part of the input signal to ground but I wouldn't know how to calculate it.

  2. Thanks for the quick replies everybody.
    I actually tried running into the inverting input and got nothing out of it.  It didn't make sense to have a 1K resistor feeding into the non-inverting input but since I didn't get a signal, I tried it the way I showed in the scheme.  Perhaps my ground on the non-inverting input was poor.  I'll give it another shot.

    Thanks again,  I was racking my brain yesterday over this.

  3. Hello.  I'm very new to electronics and have myself in an odd situation.
    I'm trying to design a simple audio amplifier to drive a VU meter based on the 4739 dual opamp because I have a bunch of them.
    I've attached a crude scheme below.

    audioscheme.gif


    What's happening is I get an audio signal, but it's always unity gain regardless of the pot position.  I know the amplifier is working because my first version ran on a 9V battery and the output was weak and distorted.  When I switched to a +-12V power supply, the signal got stronger and clearer.  If I touch anything in the feedback loop, I hear the interference.  I tried reading about op amp design but from everything I've read, I should be getting 0-10x gain.

    Like I said, I'm pretty clueless so any help will be much appreciated.

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