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CMOS diffrential pair with current mirror using active loading and unipolar power supply

Discussion in 'Power Electronics' started by Shahram Najam, Oct 15, 2016.

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  1. Shahram Najam

    Shahram Najam

    2
    0
    Oct 15, 2016
    I have been trying to construct a circuit for a week and a half now and i cannot understand why it can't seem to work. I have to design a CMOS diffretial pair with a current mirror that is not the tricky part. The hard part is that i have to use a unipolar supply to operate it. can some one help me out here? Your help would be greatly appreciated.
     
  2. TedA

    TedA

    156
    16
    Sep 26, 2011
    What have you tried so-far that does not work? You might post some schematics of the circuits you have tried. Tell us your test results for each one, particularly, just how it failed to work.

    Is this circuit being constructed from actual components, or is it being simulated?

    If you are working in the hardware domain, what components do you have on-hand?

    If you are using simulation software, what sort?

    There must be additional design requirements. It would be helpful to know what these are.

    How is this circuit to be applied or used?

    What is the desired input common mode range? Input offset voltage? Output voltage range? Power supply voltage. Power supply current? Speed, or frequency response?

    Commercial CMOS op-amps have input circuits that might serve as examples for study. Some semiconductor manufacturers provide "equivalent circuit" schematics on their data sheets.

    Ted
     
  3. Shahram Najam

    Shahram Najam

    2
    0
    Oct 15, 2016
    I have got it working.. but there is a problem. when i am applying an ac signal on both the diffrential pair, the output is 90 degree out of phase and when i am giving an ac signal at non iverting terminal and grounding the other, the output is normal. Can you help me what is the reason for this? and how can i correct this?
     
  4. TedA

    TedA

    156
    16
    Sep 26, 2011
    Sorry to always be asking for more information, but we cannot answer your question without more information from you.

    Answers to my old questions would still be useful, and we obviously need to see your circuit that is working, as well. We need not only the circuit for the amplifier itself, but also something that shows how the amplifier inputs are connected to the bias and signal sources.

    It should be possible to get 90 degree phase shift only if the test frequency is high relative to the speed of your circuit. Try a much lower test frequency. And what test frequency are you using?

    Ted
     
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