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BE3705 EXAM 2 WITH QUESTIONS AND VERIFIED ANSWERS
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BE3705 EXAM 2 WITH QUESTIONS AND VERIFIED ANSWERS...
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BE3705 EXAM 2 WITH QUESTIONS ANDVERIFIED ANSWERS
Output phase for purely resistive circuit - ANSWER zero
What are the 3 types of gains? - ANSWER Voltage, current, power
What is the benefit of expressing gain in dB? - ANSWER the dB scale compresses
the huge numeric range of gains in real systems
What dB is a gain of 1 equal to? - ANSWER 0 dB
In a two-port amplifier, why is Rin high? - ANSWER Rin needs to be high to lower
the current drawn from the input source
In a two-port amplifier, why is Rout ideally zero? - ANSWER It should be zero for
all the voltage to go to the load.
What is the benefit of using a two-port model for amplification? - ANSWER The
model simplifies amplifier behavior analysis in complex systems
Some more characteristics of two-port models include: - ANSWER linear network
models, valid only under small-signal conditions
What are the 3 characteristics of an op-amp? - ANSWER Very big Rin
Very small Rout
High gain
Three ideal op amp assumptions: - ANSWER Infinite gain
Infinite Rin
zero Ro
What does infinite Rin mean in op amps? - ANSWER No current flows into op
amp at positive or negative ports (i+ and i-=0)
In an op amp, what is the voltage difference between positive and negative ports? -
, ANSWER Zero. Voltage at each port should be the same
What is negative feedback? - ANSWER Output of op amp is fed back to the
inverting terminal. The undesirable part of the output gets smaller and smaller.
Negative feedback gives us a desirable output
What is positive feedback? - ANSWER Output of op amp is fed back through
noninverting terminal. This is usually bad because it leads to oscillations (unstable
output)
Which feedback is used for an amplifier? - ANSWER Negative feedback. You can't
have an amplifier with positive feedback.
What does an inverting amplifier look like? - ANSWER Noninverting input is
grounded
Inverting terminal is connected to output via Rf
Input is connected to inverting terminal via R1
What does the output of an inverting amplifier look like? - ANSWER The polarity
of the output is reverse of the input and there is a 180 degree phase difference
What is a virtual ground? - ANSWER Since the voltages at both ports are the same,
if one is connected to ground, the other one is at ground potential
Which of the two op amps have less drawbacks? - ANSWER Non-inverting
amplifier: the output has the same polarity as input, there is a lot more freedom in
choosing R1, no phase difference
How does noninverting amplifier configuration differ from inverting? - ANSWER
The only difference is that the input and ground are switched.
What is an op amp? - ANSWER Term for the operational amplifier chip itself. It is
not an amplifier but can be used to create an amplifier.
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