E7G: Active filters and op-amps: active audio filters; characteristics; basic circuit design; operational amplifiers
E7G01:
What determines the gain and frequency characteristics of an op-amp RC active filter?
The values of capacitors and resistors external to the op-amp
The values of capacitors and resistors built into the op-amp
The input voltage and frequency of the op-amp's DC power supply
The output voltage and smoothness of the op-amp's DC power supply
E7G02:
What causes ringing in a filter?
The frequency and phase response of the filter
The slew rate of the filter
The bandwidth of the filter
The gain of the filter
E7G03:
What are the advantages of using an op-amp instead of LC elements in an audio filter?
Op-amps exhibit gain rather than insertion loss
Op-amps are more rugged and can withstand more abuse than can LC elements
Op-amps are fixed at one frequency
Op-amps are available in more varieties than are LC elements
E7G04:
Which of the following capacitor types is best suited for use in high-stability op-amp RC active filter circuits?
Polystyrene
Electrolytic
Disc ceramic
Paper dielectric
E7G05:
How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?
Restrict both gain and Q
Restrict gain, but increase Q
Restrict Q, but increase gain
Increase both gain and Q
E7G06:
What steps are typically followed when selecting the external components for an op-amp RC active filter?
Standard capacitor values are chosen first, the resistances are calculated, and resistors of the nearest standard value are used
Standard resistor values are chosen first, the capacitances are calculated, and capacitors of the nearest standard value are used
Standard resistor and capacitor values are used, the circuit is tested, and additional resistors are added to make any needed adjustments
Standard resistor and capacitor values are used, the circuit is tested, and additional capacitors are added to make any needed adjustments
E7G07:
Which of the following is the most appropriate use of an op-amp RC active filter?
As an audio receiving filter
As a high-pass filter used to block RFI at the input to receivers
As a low-pass filter used between a transmitter and a transmission line
For smoothing power-supply output
E7G08:
Which of the following is a type of active op-amp filter circuit?
Sallen-Key
Regenerative feedback resonator
Helical resonator
Gilbert cell
E7G09:
What voltage gain can be expected from the circuit in Figure E7-4 when R1 is 10 ohms and RF is 470 ohms?
47
0.21
94
24
E7G10:
How does the gain of a theoretically ideal operational amplifier vary with frequency?
It does not vary with frequency
It increases linearly with increasing frequency
It decreases linearly with increasing frequency
It decreases logarithmically with increasing frequency
E7G11:
What will be the output voltage of the circuit shown in Figure E7-4 if R1 is 1000 ohms, RF is 10,000 ohms, and 0.23 volts is applied to the input?
-2.3 volts
0.23 volts
2.3 volts
-0.23 volts
E7G12:
What voltage gain can be expected from the circuit in Figure E7-4 when R1 is 1800 ohms and RF is 68 kilohms?
38
1
0.03
76
E7G13:
What voltage gain can be expected from the circuit in Figure E7-4 when R1 is 3300 ohms and RF is 47 kilohms?
14
28
7
0.07
E7G14:
What is an operational amplifier?
A high-gain, direct-coupled differential amplifier whose characteristics are determined by components external to the amplifier
A high-gain, direct-coupled audio amplifier whose characteristics are determined by components external to the amplifier
An amplifier used to increase the average output of frequency modulated amateur signals to the legal limit
A program subroutine that calculates the gain of an RF amplifier
E7G15:
What is meant by the term "op-amp input-offset voltage"?
The potential between the amplifier input terminals of the op-amp in a closed-loop condition
The output voltage of the op-amp minus its input voltage
The difference between the output voltage of the op-amp and the input voltage required in the immediately following stage
The potential between the amplifier input terminals of the op-amp in an open-loop condition
E7G16:
What is the typical input impedance of an integrated circuit op-amp?
Very high
100 ohms
1000 ohms
Very low
E7G17:
What is the typical output impedance of an integrated circuit op-amp?
Very low
Very high
100 ohms
1000 ohms
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