Maddox Smith Staff asked 4 years ago

Feedback Topologies

The circuit above is a relatively low-gain broad-band amplifier and employs two types of feedback topologies. The transistor parameters for both Q1 and Q2 are as follows: Β = 150 fT = 800MHz     rµ = ro = ∞     Cµ = 2.5pF      Rb = 150 (a) Identify the two types of feedback topologies employed in the circuit and the circuit elements corresponding to each of the types.                                                 [10 marks] (b) Determine the DC collector currents IC1 and IC2 of transistors Q1 and Q2, respectively. [ Hint: write down two KVL equations and solve them simultaneously]    [10 marks] (c)  Determine the closed loop gain Vo/Vs at midband frequencies. [10marks] (d)  Determine the input and output impedance of the circuit.        [10marks] (e) Estimate the bandwidth of the overall amplifier by calculating the upper 3dB frequency. [ Hint: First calculate the upper 3dB of the open loop amplifier, then apply feedback theory]