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1002 QuizEE04
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Name：
1. Draw the equivalent circuit of an OPA and list the characteristics of the ideal
Op Amp. (10 points)
2.True and False
(a) Since noise or any unwanted input signal is generally common to both inputs,
the common mode gain of a good difference amplifier should be as big as
possible.
(b) An input coupling resistance at the negative input end can reduce the
influence of voltage offset to an inverse amplifier.
(c) Virtual short or ground is a concept based on the open-loop gain of an OPA
tends to infinite.
(d) Use an op-amp IC (e.g. uA741) to design a voltage amplifier is much easy
than others transistor amplifier, since we don’t need to trade the DC biasing
problem.
(e) The output signal of a differential amplifier is vo (t )  Ad (v1  v2 )  Acm vicm , in
which the vicm represent the common mode input. The voltage gain Ad and Acm
should be as big as possible.
3. Find the output voltage in the case of the following OPA has offset voltage Vos .
R1  10k
R2  10k



R1  10k
vo
vo

R1  10k
R2  10k
R2  10k


vo

vo

4. For the difference amplifier shown in the following, let all the resistance be
100k  5% . Find an expression for the worst-case common-mode gain that
results.
5.Consider the following Op-Amp difference amplifier. Find the voltage gain
vo
vs