Homework Questions
Q1) A voltage amplifier with an input resistance of 10 kΩ, an output
resistance of 200Ω, and a gain of 1000 V/V is connected between a
100-kΩ source with an open-circuit voltage of 10 mV and a 100-Ω
load. For this situation
(a) What output voltage results?
(b) What is the voltage gain from source to load?
(c) What is the voltage gain from the amplifier input to the load?
(d) If the output voltage across the load is twice that needed and
there are signs of internal amplifier overload, suggest the location
and value of a single resistor that would produce the desired output.
Choose an arrangement that would cause minimum disruption to an
operating circuit. (Hint: Use parallel rather than series connections.)
Solution1:
Q2) A transconductance amplifier with Ri=2k Ω , Gm=40 mA/V and
Ro=20k Ω is fed with a voltage source having a source resistance of
2kΩ and is loaded with a 1k Ω resistance. Find the
voltage gain realized.
Solution2:
Q3) An amplifier with an input resistance of 10 k Ω, when driven by a
current source of 1 µA and a source resistance of 100 k Ω, has a
short-circuit output current of 10 mA and an open-circuit output
voltage of 10 V. When driving a 4-ΚΩ load, what are the values of the
voltage gain, current gain, and power gain expressed as
ratios and in dB?
Solution3
:
Q4) Figure(1) shows a signal source connected to the input of an
amplifier. Here Rs is the source resistance, and Ri and Ci are the input
resistance and input capacitance respectively, of the amplifier.
Derive an expression for Vi(s)/Vs(s) and show that it is of the lowpass STC type. Find the 3-dB frequency for the case Rs=20kΩ
Ri=80kΩ and Ci=5pF.
(Figure1)
Solution4: