13 Voltage-Voltage Feedback Sense Vout in parallelReturn Vin in series
14 Voltage-Current Feedback Sense Vout in parallelReturn current in parallelAlternative name:Return-Sense=Shunt-Shunt feedbackK has a dimension of conductance:K=IF/Vout
15 Example IRF=Vout/RF (RF is large in order to return a current) K=-1/RF (- comes from theThe direction of IF)(RF is largein order to returna current)(Open-loop gain)Assumption: RF is large!Or RF>>RD2
16 Ideal R0 Zero input impedance so that it can Measure currents as an ideal current meter.Zero output resistance so as to behaveas an ideal voltage source.
17 Calculation of Input Impedance (small resistance)
18 Example (Open loop input-impedance) R0=RD1(-gm2RD2) IRF=Vout/RF K=-1/RF
19 Calculation of Output Impedance VA=(-IF)RoRout(small resistance)(Current drawn by the feedback network is neglected)