Deck 14: Special-Purpose Op-Amp Circuits

Question 1

The input signal for an instrumentation amplifier usually comes from

A)a differential amplifier.
B)a filtered dc power supply.
C)an inverting amplifier.
D)a Wheatstone bridge.

Answer 1

D

Question 2

Refer to d)in the figure above. If Vin = 200 mV, RF = 52 k, and IEBO = 50 nA, the Vout would be

A)- 775 mV.
B)7.75 mV.
C)- 7.75 V.
D)- 5.41 mV.

Answer 2

C

Question 3

The output of a peak detector is always

A)equal to the max value of the peak level received since the last reset pulse.
B)70.7% of input.
C)equal to the min value of the peak level received since the last reset pulse.
D)None of the above.

Answer 3

A

Question 4

Refer to the figure above. Which of these circuits is known as an isolation amplifier?

A)a)
B)b)
C)c)
D)d)

Question 5

A voltage- to- current converter is used in applications where it is necessary to have an output load current that is controlled by

A)input frequency.
B)input voltage.
C)output resistance.
D)input resistance.

Question 6

The voltage gain of the input stage of an isolation amplifier is 12. If the output stage has a gain of 6, the total voltage gain is

A)144.
B)6.
C)72.
D)18.

Question 7

Isolation amplifiers can accomplish isolation using

A)transformer coupling.
B)capacitive coupling.
C)optical coupling.
D)All of the above.

Question 8

Refer to the figure above. Which of these circuits is known as an antilog amplifier?

A)a)
B)b)
C)c)
D)d)

Question 9

Instrumentation amplifiers are well suited for environments with

A)small signals superimposed on larger common- mode voltages.
B)no power supply voltages.
C)no signal and no noise.
D)high signal levels that need to be attenuated.

Question 10

An instrumentation amplifier has a high

A)power gain.
B)supply voltage.
C)CMRR.
D)output impedance.

Question 11

What is the required value of feedback resistance needed in a current- to- voltage converter where each 100 µA of input current needs to result in an output of 1 V?

A)1 M▲
B)1 k▲
C)10 k▲
D)10 M▲

Question 12

When using an OTA in a Schmitt- trigger configuration, the trigger points are controlled by

A)the IOUT.
B)the IBIAS.
C)the VOUT.
D)Both A and B above.

Question 13

Refer to the figure above. Which of these circuits is known as a voltage- to- current converter?

A)a)
B)b)
C)c)
D)d)

Question 14

Refer to a)in the figure above. If R1 = R2 = 28 k▲ and RG = 100 ▲, the Acl would be

A)560.
B)561.
C)5.60.
D)56.1.

Question 15

Which of the following correctly describes the relationship between bandwidth and gain for an instrumentation amplifier?

A)Bandwidth decreases as gain increases.
B)Bandwidth and gain are both zero.
C)Instrumentation amplifiers have no bandwidth since they can only amplify dc.
D)Bandwidth increases as gain increases.

Question 16

Log amplifiers are used to

A)perform analog multiplication and division.
B)compress an analog signal.
C)linearize an exponential output from a transducer.
D)All of the above.

Question 17

The primary function of the oscillator in an isolation amplifier is to

A)produce dual polarity dc voltages for the input to the demodulator.
B)convert dc to low frequency ac.
C)convert dc to high frequency ac.
D)rectify high frequency ac to dc.

Question 18

The current applied to a current- to- voltage converter circuit changes from 4 to 20 mA. If Rf is 625 ▲, what is the change in output voltage?

A)5 V
B)20 V
C)1 V
D)10 V

Question 19

If an operational transconductance amplifier OTA)is used as a nonlinear mixer and an audio signal is mixed with an RF signal, the output will be an)signal.

A)square wave
B)frequency modulated FM)
C)triangular wave
D)amplitude modulated AM)

Question 20

Refer to the figure above. Which of these circuits contains an OTA?

A)a)
B)b)
C)c)
D)d)

Question 21

Refer to b)in the figure above. If RL = 20 k, R1 = 1.2 k, and Vin = 2.5 V, the load current IL would be

A)2.083 A.
B)208.3 µA.
C)2.083 mA.
D)20.83 mA.

Question 22

The OTA has a input impedance and a CMRR.

A)low, high
B)high, high
C)high, low

Question 23

An input transducer converts

A)a nonelectrical quantity to an electrical quantity.
B)an electrical quantity to a nonelectrical quantity.
C)voltage to current.
D)current to voltage.

Question 24

The total voltage gain of an isolation amplifier is 49. If the voltage gain of the input and output stages are equal, the voltage gain for each stage is

A)4.9.
B)98.
C)7.
D)24.5.

Question 25

Refer to the figure above. Which of these circuits is known as a peak detector?

A)a)
B)b)
C)c)
D)d)

Question 26

Refer to the figure above. Which of these circuits is known as a constant- current source?

A)a)
B)b)
C)c)
D)d)

Question 27

To scale down large signal voltages without obscuring lower signal voltages, should be used.

A)logarithmic signal compression
B)antilogarithmic signal compression
C)signal compression
D)natural logarithmic signal compression

Question 28

In some respects an isolation amplifier is nothing more than an elaborate

A)instrumentation amplifier.
B)op- amp.
C)rectifier and filter.
D)Both A and B above.

Question 29

Refer to a)in the figure above. If R1 = R2 = 30 k▲ and the closed loop gain is 450, the value of the external gain- setting resistor RG is

A)133.63 ▲.
B)13.36 ▲.
C)133.63 k▲.
D)None of the above.

Question 30

An antilog amplifier is formed by connecting a pn junction diode or BJT)to the

A)output.
B)inverting and noninverting inputs.
C)feedback loop.
D)input.