Q: Given an op-amp with an open-loop gain $$A_0$$ = $$10^5$$ and a supply voltage of $$\pm 9.0\ \mathrm{V}$$, what is the minimum input voltage difference $$(V^+ - V^-)$$ required to saturate the output?

$$9.0 \times 10$$^{-5}$$\ \mathrm{V}$$

Question 1

Which of the following is NOT a property of an ideal operational amplifier (op-amp)?

Accepted Answer

Limited bandwidth

Question 2

A real op-amp typically has an input impedance between which of the following values?

Accepted Answer

$$10^{10}$$ \ \Omega$$ and 10$$^{12}$$ \ \Omega$$

Question 3

Given an op-amp with an open-loop gain $$A_0$$ = $$10^5$$ and a supply voltage of $$\pm 9.0\ \mathrm{V}$$, what is the minimum input voltage difference $$(V^+ - V^-)$$ required to saturate the output?

Accepted Answer

$$9.0 	imes 10$$^{-5}$$\ \mathrm{V}$$

Question 4

Which equation correctly describes the output voltage of an op-amp in open-loop configuration?

Accepted Answer

$$V_{out} = A_0$ (V^+ - V^-)$$

Question 5

In a comparator circuit using an op-amp, what happens when $$V^+ \u003e V^-$$?

Accepted Answer

The output voltage is positive and saturated

Question 6

A non-inverting amplifier has $$R_f = 10\ \mathrm{k\Omega}$$ and $$R_{in} = 2\ \mathrm{k\Omega}. $$What is its voltage gain $$A_0$$?

Accepted Answer

$$A_0 = 6$

Question 7

For the inverting amplifier circuit, which formula gives the voltage gain $$A_0$$?

Accepted Answer

$$A_0$$ = -\frac{R_f}{R_{in}}$$

Question 8

A light-dependent resistor (LDR) is used in an op-amp circuit to monitor light intensity. As the lamp is moved away from the LDR, what happens to the output voltage?

Accepted Answer

The output voltage becomes more negative

Question 9

Which of the following is a benefit of negative feedback in an op-amp circuit?

Accepted Answer

Greater operating stability

Question 10

A relay is used as an output device in an op-amp circuit. What is its primary function?

Accepted Answer

To convert a small current to switch a larger current

Question 11

A thermistor is used as a sensing device in an op-amp circuit. What property does it monitor?

Accepted Answer

Temperature

Question 12

In a non-inverting amplifier, if $$V_{in} = 0.50\ \mathrm{V}$$, $$R_f = 40\ \mathrm{k\Omega}$$, $$R_{in} = 10\ \mathrm{k\Omega}$$, and the supply voltage is $$\pm 9.0\ \mathrm{V}$$, what is $$V_{out}$$?

Accepted Answer

$$V_{out} = 2.5\ \mathrm{V}$$

Question 13

Which device changes its resistance with strain and is commonly used in sensing applications?

Accepted Answer

Strain gauge

Question 14

A piezo-electric transducer is used in a sensor circuit. What does it produce in response to sound pressure?

Accepted Answer

A voltage

Question 15

If an inverting amplifier has $$R_f = 22\ \mathrm{k\Omega}$$, $$R_{in} = 10\ \mathrm{k\Omega}$$, and $$V_{in} = 0.44\ \mathrm{V}$$, what is $$V_{out}$$?

Accepted Answer

$$V_{out} = -0.968\ \mathrm{V}$$

Question 16

Which of the following best describes the function of an LED in an op-amp output circuit?

Accepted Answer

It emits light when a current flows through it

Question 17

In a feedback amplifier, the overall voltage gain with feedback is given by which formula?

Accepted Answer

$$A = \frac{A_0$}{1 - A_0$ \beta}$$

Question 18

A block diagram for an electronic sensor includes three main stages. Which is the correct order?

Accepted Answer

Sensing device → Processing unit → Output device

Question 19

Which of the following statements about the slew rate of an ideal op-amp is correct?

Accepted Answer

It is infinite, so there is no delay between input and output changes

Question 20

In a comparator circuit with two LEDs (red and green) connected to the output, what happens when the input voltage is positive?

Accepted Answer

Only the red LED lights up

Operational Amplifiers and Output Devices in Electronics

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