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Transistor Biasing

Discussion in 'Electronics Homework Help' started by BlackMelon, Apr 28, 2017.

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  1. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    Hello,

    I'm trying to give a voltage Vb1 and Vb2 in the figure. What circuit topology do I have to use for this?

    Thank You,
    BlackMelon
     

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,350
    2,255
    Nov 17, 2011
    Huh?
    Any voltage source will do, even a simple resistive divider as the load by the gates is negligible to non-present.

    Could you detail your idea a bit more?
     
  3. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    I am trying to design an op-amp with specifications shown in the pdf file. I can use any topologies I want. But I am allowed to use only one voltage source. Is there any techniques to bias that point?

    PS. I think using voltage dividers might get me in trouble after this. Because I have to play with (W/L) ratio to have a specified gain, forcing me to change the resistors in the dividers for new Vgs too. Do you think so? Or is this already the easiest way to do?
     

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  4. Harald Kapp

    Harald Kapp Moderator Moderator

    10,350
    2,255
    Nov 17, 2011
    You could use a MOSFET based voltage reference. But that's probably cracking a nut with a sledgehammer. The accuracy of a resistive divider is probably sufficient in this application.
    If you need to change VGS for whatever reason, any circuit you use wiil have to be adjusted, be it a resistive divider or a voltage reference circuit.
    When you build the resistors from MOSFETs, you can scale them together with the other MOSFETs, that may (or may not - I'm not deep into your circuit) help lessen the workload.
     
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