Amplifier feedback topology

Discussion in 'Homework Help' started by ridefun2, Apr 20, 2011.

  1. ridefun2

    Thread Starter New Member

    Apr 20, 2011
    I'm need to determine the feedback topology of the circuit in the picture. I'm thinking it's a series-series design, with the sampled variable being the current through RL and the feedback signal being the voltage at the node between R1 and R2. Am I correct?

  2. JDT

    Well-Known Member

    Feb 12, 2009
    The sampled variable is the voltage across "r". This is proportional to the current in RL

    RL is inside the feedback loop and the voltage developed across it (due to its resistance) will not effect the current passing through it (due to the feedback). So effectively, RL is being driven by a constant-current. This is providing that the amplifier can supply the voltage.

    The gain of the amplifier (normally very high) will ensure that the voltage at the junction of R1 and R2 will equal V1. Or to put it another way, the gain of the amplifier tries to make the voltage between the inverting and non-inverting inputs = 0.