Op-Amp Voltage Follower With Bootstrap???

Discussion in 'Homework Help' started by diya khan, Nov 28, 2011.

  1. diya khan

    Thread Starter New Member

    Nov 29, 2010

    can anyone please explain me the operation and purpose of this Op-Amp Voltage Follower With Bootstrap!

  2. nuckollsr


    Dec 17, 2009
    If the capacitor were left out, you see the classic gain-of-one, non-inverting amplifier. The input impedance of the circuit would be the parallel values of the bias resistor to ground (in this case 200K) and the very high input impedance of the amplifier. When the capacitor is added, the AC input impedance of the circuit rises to a very high value because the bottom end of the upper bias resistor now "wiggles" in synchronization with the output of the amplifier. Hence, no signal current is impressed across the 100K resistor while the pair of resistors maintain a DC reference for the amplifier's input pin. The bootstrap makes the DC bias network 'disappear' with respect to applied signal.