Study Amateur Extra E7G

E7G

PRACTICAL CIRCUITS

Operational amplifiers: characteristics and applications

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E7G01

What is the typical output impedance of an op-amp?

  1. A Very low
  2. B Very high
  3. C 100 ohms
  4. D 10,000 ohms
E7G02

What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?

  1. A High-pass filter
  2. B Low-pass filter
  3. C Band-pass filter
  4. D Notch filter
E7G03

What is the typical input impedance of an op-amp?

  1. A 100 ohms
  2. B 10,000 ohms
  3. C Very low
  4. D Very high
E7G04

What is meant by the term "op-amp input offset voltage"?

  1. A The output voltage of the op-amp minus its input voltage
  2. B The difference between the output voltage of the op-amp and the input voltage required in the immediately following stage
  3. C The differential input voltage needed to bring the open loop output voltage to zero
  4. D The potential between the amplifier input terminals of the op-amp in an open loop condition
E7G05

How can unwanted ringing and audio instability be prevented in an op-amp audio filter?

  1. A Restrict both gain and Q
  2. B Restrict gain but increase Q
  3. C Restrict Q but increase gain
  4. D Increase both gain and Q
E7G06

What is the gain-bandwidth of an operational amplifier?

  1. A The maximum frequency for a filter circuit using that type of amplifier
  2. B The frequency at which the open-loop gain of the amplifier equals one
  3. C The gain of the amplifier at a filter's cutoff frequency
  4. D The frequency at which the amplifier's offset voltage is zero
E7G07

What voltage gain can be expected from the circuit in Figure E73 when R1 is 10 ohms and RF is 470 ohms?

  1. A 0.21
  2. B 4700
  3. C 47
  4. D 24
E7G08

How does the gain of an ideal operational amplifier vary with frequency?

  1. A It increases linearly with increasing frequency
  2. B It decreases linearly with increasing frequency
  3. C It decreases logarithmically with increasing frequency
  4. D It does not vary with frequency
E7G09

What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1,000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?

Figure E7-3 from the NCVEC question pool
  1. A 0.23 volts
  2. B 2.3 volts
  3. C -0.23 volts
  4. D -2.3 volts
E7G10

What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 1,800 ohms and RF is 68 kilohms?

Figure E7-3 from the NCVEC question pool
  1. A 1
  2. B 0.03
  3. C 38
  4. D 76
E7G11

What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?

Figure E7-3 from the NCVEC question pool
  1. A 28
  2. B 14
  3. C 7
  4. D 0.07
E7G12

What is an operational amplifier?

  1. A A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance
  2. B A digital audio amplifier whose characteristics are determined by components external to the amplifier
  3. C An amplifier used to increase the average output of frequency modulated amateur signals to the legal limit
  4. D A RF amplifier used in the UHF and microwave regions
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