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Op Amp Fundamentals and Noise and Signal Integrity
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1
Question
What is the output when an op-amp is configured in open-loop?
Answer
High gain with no feedback; output saturates to rails
2
Question
In a noninverting op-amp, what is the relationship between input and output polarity?
Answer
Output follows input polarity (same phase)
3
Question
Given an inverting amplifier with no resistor values specified, what is the general sign of the output relative to the input?
Answer
Output is inverted relative to the input
4
Question
What term best describes the major source of interference with a desired signal in electronic systems?
Answer
Noise signal
5
Question
If the feedback resistor in a noninverting op-amp circuit is opened, what happens to the closed-loop gain?
Answer
Gain increases
6
Question
Which plot is used to determine the stability of an op-amp?
Answer
Bode plot
7
Question
In AC analysis of networks using Bode plots, how many plot types can be obtained?
Answer
Three
8
Question
What happens to gain when the operating frequency of an op-amp increases?
Answer
Gain decreases and phase shift increases
9
Question
What is the typical range for signals a preamplifier must handle in audio applications?
Answer
20 Hz to 20 kHz
10
Question
Which device is used to convert irregularly shaped waveforms to regular shaped waveforms?
Answer
Schmitt trigger
11
Question
What does a voltage follower primarily do in op-amp circuits?
Answer
Provides unity gain (gain = 1) and high input impedance
12
Question
What is the primary function of a pre-amplifier in a signal chain?
Answer
Boost a weak signal to a usable level for later stages
13
Question
What figure is used to quantify how much noise a receiver adds relative to its ideal performance?
Answer
Noise figure
14
Question
Which audio microphone type typically has high input impedance and high sensitivity?
Answer
Condenser microphone
15
Question
Which microphone type typically has high output impedance and moderate sensitivity?
Answer
Dynamic (magnetic) microphone
16
Question
If an op-amp has infinite gain and infinite bandwidth, what characteristic is violated in practice?
Answer
Finite slew rate and output limitations; real op-amps cannot have infinite bandwidth
17
Question
What is the effect of negative feedback on an op-amp’s linear operation?
Answer
Enables linear operation by reducing gain variation and stabilizing behavior
18
Question
In a differential amplifier, what is the output in an open-loop configuration relative to the input difference?
Answer
Output proportional to the difference between the inputs multiplied by gain
19
Question
What is the unit of power gain measured in decibels?
Answer
dB
20
Question
What happens to the op-amp output in an open-loop configuration when any small input exceeds zero?
Answer
Output saturates at one of the supply rails
21
Question
What is CMRR in op-amps and what does a higher value signify?
Answer
Common-Mode Rejection Ratio; higher means better suppression of common-mode signals
22
Question
What is the effect of opening the feedback path on the gain of a differential amplifier?
Answer
Gain approaches the open-loop high gain value
23
Question
In a non-inverting amplifier, how is the input connected relative to the inverting input?
Answer
Input is applied to the non-inverting input; the inverting input is fed back from the output
24
Question
What is the hallmark of a unity-gain buffer (voltage follower)?
Answer
Voltage gain of 1; high input impedance; low output impedance
25
Question
Why are open-loop op-amp configurations not used in linear applications?
Answer
Because they saturate easily and cannot produce a stable linear output