Signals and Amplifiers topics include: The basics of signals, amplifiers, sinusoidal steady state analysis, amplifier circuit models and frequency response. A signal amplifier is a circuit that uses electrical power to increase the amplitude of an incoming signal voltage or current signal. The output terminals of the signal amplifier output the higher amplitude version.  Here are some types of amplifiers: Small signal amplifiers: Also called voltage amplifiers, these amplifiers amplify an input voltage to a higher output voltage. However, the output may not have enough power to drive loads... Show more

Signals and Amplifiers topics include: The basics of signals, amplifiers, sinusoidal steady state analysis, amplifier circuit models and frequency response.

A signal amplifier is a circuit that uses electrical power to increase the amplitude of an incoming signal voltage or current signal. The output terminals of the signal amplifier output the higher amplitude version. 

Here are some types of amplifiers:
Small signal amplifiers: Also called voltage amplifiers, these amplifiers amplify an input voltage to a higher output voltage. However, the output may not have enough power to drive loads like motors and loudspeakers.
Power amplifiers: This subtype of amplifier raises the power of a signal. They are used in modern consumer electronic devices such as smartphones and tablets.
RF amplifiers: These tuned amplifiers convert the input signal into an output signal that provides the required response at a given frequency.
Differential amplifiers: These amplifiers amplify the difference of the two signals applied to its input. They are subtractor circuits that subtract the two applied input and then produce amplified output.
Current amplifiers: These amplifiers increase the current of an input signal. They are often used in power electronic systems, such as in power supplies or motor controllers.
Transistor amplifiers: These amplifiers are fully reliant on transistors. They can use a current, voltage, or power signal as the input signal. The signal is amplified without affecting its properties, and the output is a modified version of the original signal. 

Show less

Electronic Devices and Circuits Practice Test: Signals and Amplifiers

Time left 00:00

25 Questions

1. Consider the DAC (digital to Analog Converter) shown below. Where b₁, b₂….b_n can be either 0 or 1. For v_ref = 10V, n = 6, and R= 5000 ohm, which of the following is true?

The maximum value of the output current is 1.9375 mAThe change in the output current if the LSB is changed from 0 to 1 is 0.03125 mAThe change in the output current is the MSB is change from 0 to 1 is 0.5 mANone of these

2. Vc(t) = ?

0.89 cos (1000t + 63.43) V0.89 cos (1000t – 63.43) V0.45 cos (1000t + 26.57) V0.45 cos (1000t – 26.57) V

3. i(t) = ?

2 sin (2t 5.77) Acos (2t 84.23) A

4. The ratio of the open circuit voltage of a voltage amplifier (A_V) to the short circuit transconductance of a (G_m) of a transconductance amplifier, given that both have the same value of the internal resistance (R_i) and the output resistance (R₀), is

R01/R01/RiRi

5. Statement 1: Voltage gain of -5 means that the output voltage has been attenuated.
Statement 2: Voltage gain of -5db means that the output voltage has been attenuated.

Statement 1 and Statement 2 are falseStatement 1 and Statement 2 are trueOnly Statement 2 is trueOnly Statement 1 is true

6. The output voltage of a voltage amplifier has been found to decrease by 20% when a load resistance of 1 kΩ is connected. What is the value of the amplifier output resistance?

200Ω250Ω350Ω50Ω

7. Symmetrically saturated amplifiers operating in clipping mode can be used to convert a sine wave to a

Square waveTriangular wavePseudo Square waveSawtooth wave

8. What is meant by stability of the an amplified signal?

The amplified signal should not have self oscillationThe ratio of the input and the output signal must be finiteThe input and the output signal must be proportionalThe amplified signal must have a finite amplitude

9. In compact disc (CD) audio technology, the signal is sampled at 44kHz. Each sample is represented by 16bits. What is the speed of the system in bits/second?

1,441,792,000 bits/second2,750 bits/second704,000 bits/second1.34 bits/second

10. Which of the following is a transresistance amplifier?

11. The ideal values for the input resistance (Ri) and the output resistance (Ro) of a transconductance amplifier are

Ri = ∞ and Ri = 0Ri = 0 and R0 = ∞Ri = ∞ and R0 = ∞Ri = 0 and Ro = 0

12. The signal whose waveform is not effected by a linear circuit is

Sine/Cosine wave signalSawtooth waveform signalRectangular waveform signalTriangular Waveform signal

13. Which of the following is true?

Coupling capacitors causes the gain to fall off at high frequenciesAll of the mentionedNone of theseInternal capacitor of a device causes the gain to fall off at low frequencies

14. An amplifier has a voltage gain of 40db. The value of A_VO is

2010010200

15. An amplifier has a voltage gain of 100 V/V and a current gain of 1000A/A. the value of the power gain decibel is

30 db50 db60 db40 db

16. The voltage gain of the amplifier is 8 and the current gain is 7. The power gain of the amplifier is

34.963 db56 db1 db17.481 db

17. i2(t) = ?

2.04 cos (4t 92.13) A2.04 cos (4t 2.13) A2.04 sin (4t 92.13) A2.04 sin (4t 2.13) A

18. Under what condition can the circuit shown be called a compensated attenuator.

C1R1 = C2R2C1C2 = R1R2R1 = 0C1R2 = C2R1

19. The units of voltage gain is

It has no units, it is a ratioAll of the mentionedNone of theseDecibels (db)

20. A transconductance amplifier with Ri = 2 kΩ, Gm = 40 mA/V, and Ro = 20 kΩ is fed with a voltage source having a source resistance of 2 kΩ and is loaded with a 1-kΩ resistance. Find the voltage gain realized.

19.05 V/V21.05V/V18.05 V/V20.05 V/V

21. Consider the DAC (digital to Analog Converter) shown below. Where b₁, b₂….b_n can be either 0 or 1. Which is the Most Significant Bit and Least Significant Bit in this case?

MSB: b1, LSB: bNMSB: bN, LSB: bNMSB: b1, LSB: b1MSB: bN, LSB: b1

22. A cosine wave voltage signal has a 10V RMS value and 60Hz frequency. Also at time, t=0, the value of the voltage signal is equal to its RMS value. Which of the following is the correct mathematical representation of the voltage signal?

10 cos(60t)14.14 cos(60t + π/4)10 cos (120πt)14.14 cos(120πt + π/4)

23. Consider a voltage amplifier having a frequency response of the low-pass STC type with a dc gain of 60 dB and a 3-dB frequency of 1000 Hz. Then the gain db at

f = 1Mhz is 0 dbf = 10 Hz is 55 dbf = 100 kHz is 25 dbf = 10 kHz is 45 db

24. You are given two amplifiers, A and B, to connect in cascade between a 10-mV, 100-kΩ source (S) and a 100-Ω load (L). The amplifiers have voltage gain, input resistance, and output resistance as follows: for A, 100 V/V, 10 kΩ, 10 kΩ, respectively; for B, 1 V/V, 100 kΩ, 100 Ω, respectively. Your problem is to decide how the amplifiers should be connected so that the voltage gain is maximum.

SABLNone as neither combination is able to amplify the input signalBoth have the same voltage gainSBAL

25. General representation of the frequency response curve is called

Bode PlotMiller PlotBandwidth PlotThevenin Plot