phase margin in opamp circuit

Discussion in 'General Electronics Chat' started by evgenii, Jun 15, 2009.

  1. evgenii

    Thread Starter New Member

    Jun 15, 2009
    2
    0
    Hi!
    Cmos opamp (repeater) has output on I/O pad. Complex capacitance of this pad may has different amount, say, 10-15pF. How to disable auto-oscillations of this repeater w/o using big internal miller cap...:(
    Thanks!:)
     
  2. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Are you perhaps talking about a buffer, or what is the purpose of the op-amp?

    If it IS a buffer, a resistor (eg. 10..100 Ohm) can be put in-line with the output and the feedback to the inverting pin is then taken after the resistor (contrary to directly at the op-amp output).
     
  3. evgenii

    Thread Starter New Member

    Jun 15, 2009
    2
    0
    Thanks for you reply!
    This is a repeater for current source. Current may be chosen by different R load and always stable V_ref. R load range : 3KOhm - 300kOhm. Vref range : 0.25 V - (VDD - 2) V. Repeater output may has different C_load...
    Miller cap, for example, on cmos transistor, has very big chip area....
     
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