nmos current mirror with differential pair

Discussion in 'General Electronics Chat' started by leo47, Jun 5, 2006.

  1. leo47

    Thread Starter New Member

    Jun 5, 2006
    Why is it better to use a differential pair to guide the current to the output node, rather then using just one simple switch?
    Anyone an idea?
    I made a current steering dac and somebody asked me that question but I just took the diff. pair because everbody uses it, i don't know why it is better.
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    If you really use complementary switching signals for V1 and V2, you can use lower peak-to peak input signal swings, the voltage across the current source M3-M4 doesn't change (yielding temperature stability and faster output settling), you will get outputs that are "complementary", and there will be minimal (zero, ideally) change in IDD, which keeps supply noise to a minimum.
    In the Electro-Tech forum, I missed your statement that this was in a current-steering DAC. Sorry about that.