What would be the basic amplifier circuit for these feedback amplifiers?

Discussion in 'Homework Help' started by Shubhi, Apr 8, 2015.

  1. Shubhi

    Thread Starter New Member

    Apr 8, 2015
    Fig 1 shows the first feedback amplifier circuit.

    My Attempt..

    First, I found the topology to be - Voltage Series, as the output and feedback are taken from same nodes (voltage sampling) & input and feedback are from different nodes (series mixing).
    Any other explanation for topology is welcomed.

    Then I made the Input circuit (without feedback),fig 2, by taking V0 =0 and output circuit (without feedback), fig. 3, by taking Ii =0.

    Now in the final circuit, that we obtain by adding both input circiut and output circiut, according to me in input circuit as there is Rc connected to the collector at one end and to +Vcc at other, and in output the Rc is connected one end to +Vcc and to Re, So the final circuit should look like Fig. 4
    But what our teacher agrees to is Fig 5, and I don't really find her explanation concrete (Where would +Vcc lie in fig 5?)

    As for the circuit in figure 6, I have no idea where to start from.

    I seek help regarding the explanation and construction of the basic amplifier circuit of fig. 1 and fig 6.

    PS: +Vcc is the biasing voltage to keep transistor in active mode.
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  2. hobbyist

    Distinguished Member

    Aug 10, 2008
    It's been so long that I learned this stuff, so you are probable more up to date with this than I am, but I'll try to help out the best I can from what I learned,
    If I'm remembering this correctly, "series feedback is so called because the input signal is in series with the feedback component, RE. RE provides current feedback as current is the common in a series circuit.

    With that in mind, I think your fig. 3 may be incorrect, because RE needs to be present for feedback to be realized, and your calling fig. 3 "Without feedback"
    RE would need to be removed to have it "without" feedback.

    In fig 6. determine what the base bias is for the input transistor, and how is its bias voltages affected with respect to current flow through the emitter resistor of the output transistor.