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Op amp/Zener voltage clamper problem

Discussion in 'General Electronics Discussion' started by Satindas, Jan 7, 2012.

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  1. Satindas


    Jan 7, 2012
    I'm at the breadboard stage of a 4 channel Arduino cv quantizer which is all going pretty well so far except for one small problem which I can't solve.
    The cv inputs need to be clamped to 5V and this is the circuit:


    it simulates fine but on the breadboard even with nothing connected I get 0.27V at the output which is like messing up the whole thing. I've checked everything a zillion times and now my head hertz.
    Please help :)


    Attached Files:

  2. Resqueline


    Jul 31, 2009
    As far a I can understand the max output voltage can be Vdd - 9.7V, and negative inputs are clipped. Otherwise the output follows the input.
    I other words; the 5V clamping effect requires a regulated +/- 15V op-amp supply.
    So, what's your power supply (a single 9V I guess?), and what op-amp are you using?
  3. Laplace


    Apr 4, 2010
    It appears there are two back-to-back diodes in series, so unless the opamp output exceeds 9 V there is nothing reaching the circuit output terminal except leakage from the '-' input terminal. Try disconnecting the diode from the opamp output and see if there is any variation in the 0.27 V.
  4. Satindas


    Jan 7, 2012
    Thanks guys I got this sorted.....a duff TL074 screwed my weekend but I learnt much along the way. ;-)
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