how to analyze the bandwidth of current mode circuit

Discussion in 'General Electronics Chat' started by matrixon, Jan 10, 2016.

  1. matrixon

    Thread Starter New Member

    Dec 22, 2015
    In voltage mode operation,the impedance(R parallel C) of a node will decrease as the signal freq increases with the current(I) flowing through unchanged.So according to V=ZI,the voltage at that node is degraded 3dB/dec at the signal freq at 1/RC.(assume the node has domonant pole)

    But how about the analysis of current mode circuit?How to define the BW of a current mode circuit(EX:current conveyor,CFA)?Does a current amp have BW?
    (My partner says that the BW of a current mode circuit is unit gain bandwidth,but I don't understand)
  2. crutschow


    Mar 14, 2008
    A current-mode op amp does have a bandwidth as defined in its data sheet but it's not greatly affected by the closed-loop gain so it doesn't have a gain-bandwidth product value like a voltage-mode op amp.
    That's because a current-mode op amp doesn't require the single-pole internal roll-off for compensation that a voltage-mode op amp does.

    Incidentally a single-pole RC circuit has a voltage rolloff of 6dB/octave or 20dB/decade , not 3dB.
  3. sailorjoe

    Active Member

    Jun 4, 2013