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
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    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

    Expert

    Mar 14, 2008
    12,991
    3,227
    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

    Member

    Jun 4, 2013
    361
    63
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