Electronics Engineering Multiple Choice Questions and Answers (MCQs) Part 6:
241. The voltage follower is commonly used as
(a) Switch.
(b) Isolator.
(c) Regulator.
(d) None of these.
Answer : (b) Isolator.
242. A voltage-to-current op-amp converter is also called as
(a) transconductance amplifier.
(b) transresistance amplifier.
(c) ideal voltage amplifier.
(d) ideal current amplifier.
Answer : (a) transconductance amplifier.
243. The main advantage in using a three OP-AMP instrumentation amplifier over a single OP-AMP differential amplifier lies in
(a) higher values of CMRR.
(b) lower noise figure.
(c) elimination of the need for accurate matching of resistors.
(d) simplicity of gain adjustment.
Answer : (c) elimination of the need for accurate matching of resistors.
244. A comparator with hysteresis
(a) has one trigger point.
(b) has two trigger points.
(c) has a variable trigger point.
(d) is like a magnetic circuit.
Answer : (b) has two trigger points.
245. The zero level detector is one application of a
(a) differentiator.
(b) integrator.
(c) summing amplifier.
(d) comparator.
Answer : (d) comparator.
246. A triangular-square wave generator uses
(a) a sine wave oscillation and a comparator.
(b) an integrator and a comparator.
(c) a differentiator and a comparator.
(d) a sine wave oscillator and a clipper.
Answer : (b) an integrator and a comparator.
247. A triangular wave can be generated by
(a) integrating a square wave.
(b) differentiating a square wave.
(c) integrating a sine wave.
(d) differentiating a sine wave.
Answer : (a) integrating a square wave.
248. If the input to a log amplifier is x, the output is proportional to
(a) 2.3 log10x
(b) log x
(c) log10x
(d) log x and 2.3 log10x
Answer : (b) log x
249. If the input to an antilog amplifier is x, the output is proportional to
(a) eIn x
(b) ex
(c) In x
(d) e-x
Answer : (a) eIn x
250. In order to rectify sinusoidal signals of millivolt range (< 0.6 V)
(a) bridge rectifier using diodes can be employed.
(b) full-wave diode rectifier can be used.
(c) a diode is to be inserted in the feedback loop of an OP-AMP.
(d) a diode is to be inserted in the input of an OP-AMP.
Answer : (c) a diode is to be inserted in the feedback loop of an OP-AMP.
251. The most commonly used amplifier in sample and hold circuits is
(a) a unity gain inverting amplifier.
(b) a unity gain noninverting amplifier.
(c) an inverting amplifier with a gain of 10.
(d) an inverting amplifier with a gain of 100.
Answer : (b) a unity gain noninverting amplifier.
252. For a given sample-and-hold circuit, if the value of the hold capacitor is increased, then
(a) droop rate decreases and acquisition time decreases.
(b) droop rate decreases and acquisition time increases.
(c) droop rate increases and acquisition time decreases.
(d) droop rate increases and acquisition time increases.
Answer : (b) droop rate decreases and acquisition time increases.
253. ICL 8038 is capable of generating
(a) sine wave only.
(b) square wave and triangular wave.
(c) sine, square and triangular waves.
(d) sine and triangular waves.
Answer : (c) sine, square and triangular waves.
254. The lower threshold voltage VLT and upper threshold voltage for IC-555 timer are respectively
(a) 1/3 VCC, 2/3 VCC
(b) 2/3 VCC, 1/3 VCC
(c) 1/2 VCC, 1/3 VCC
(d) 1/3 VCC, 1/2 VCC
Answer : (a) 1/3 VCC, 2/3 VCC
255. Consider the following statements:
The 555 timer can be employed in
1. a monostable multivibrator.
2. a bistable multivibrator.
3. an astable multivibrator.
Of the statements
(a) 1 and 2 are correct.
(b) 1 and 3 are correct.
(c) 2 and 3 are correct.
(d) 1, 2 and 3 are correct.
Answer : (b) 1 and 3 are correct.
256. Which one of the following sets of circuits can be obtained by using a 555 timer?
(a) Pulse modulator and amplitude demodulator.
(b) Pulse modulator and astable multivibrator.
(c) Amplifier demodulator and ac to dc converter.
(d) AC to dc converter and astable multivibrator.
Answer : (b) Pulse modulator and astable multivibrator.
257. The main advantage of active filter is that it can be realized without using
(a) transistor.
(b) capacitor.
(c) resistor.
(d) inductor.
Answer : (d) inductor.
258. Which one of the following is true for narrow bandpass filter?
(a) Q < 10.
(b) Q > 10.
(c) Q < 5.
(d) Q = 1.
Answer : (b) Q > 10.
259. The essential blocks of a phase lock loop (PLL) are phase detector, amplifier
(a) high-pass filter and crystal controlled oscillator.
(b) low-pass filter and crystal controlled oscillator.
(c) high-pass filter and voltage controlled oscillator.
(d) low-pass filter and voltage controlled oscillator.
Answer : (d) low-pass filter and voltage controlled oscillator.
260. An oscillator whose frequency is changed by a variable dc voltage, is known as
(a) a crystal oscillator.
(b) a VCO.
(c) an Armstrong oscillator.
(d) a piezoelectric device.
Answer : (b) a VCO.
261. All of the following are parts of a basic voltage regulator except
(a) control element.
(b) sampling circuit.
(c) voltage follower.
(d) error detector.
Answer : (b) sampling circuit.
262. Which one of the following statements is correct ?
In the case of load regulation
(a) when the temperature changes the output voltage remains constant.
(b) when the input voltage changes, the load current remains constant.
(c) when the load changes, the load current remains constant.
(d) when the load changes, the output voltage remains constant.
Answer : (d) when the load changes, the output voltage remains constant.
263. Which one of the following statements is correct ?
An ideal regulated power supply should have
(a) 100% regulation.
(b) 50% regulation.
(c) 0% regulation.
(d) 75% regulation.
Answer : (c) 0% regulation.
264. In a linear regulator, the control transistor is conducting
(a) a small part of the time.
(b) half of the time.
(c) all the time.
(d) only when load current is excessive.
Answer : (c) all the time.
265. The basic difference between a series regulator and a shunt regulator is
(a) the amount of current that can be handled.
(b) the position of control element.
(c) the type of sample circuit.
(d) the type of error detector.
Answer : (b) the position of control element.
266. Consider the following statements :
Switched mode power supplies are preferred over the continuous type, because they are
1. suitable for use in both ac and dc.
2. more efficient.
3. suitable for low-power circuits.
4. suitable for high-power circuits.
Of these statements.
(a) 1 and 2 are correct.
(b) 1 and 3 are correct.
(c) 2 and 3 are correct.
(d) 2 and 4 are correct.
Answer : (c) 2 and 3 are correct.
267. The most suitable device for high frequency inversion in SMPS is
(a) BJT.
(b) IGBT.
(c) MOSFET.
(d) GTO.
Answer : (c) MOSFET.
268. In a switching regulator, the control transistor is conducting
(a) part of the time.
(b) all of the time.
(c) only when the input voltage exceeds a set limit.
(d) only when there is an overload.
Answer : (a) part of the time.
269. In a switched-mode power supply (SMPS), after conversion of ac supply to a highly filtered dc voltage, a switching transistor is switched on and off at a very high speed by a pulse width modulator (PWM) which generates a very-high frequency square pulses. The frequency of the pulses is typically in the range of
(a) 100 Hz-200 Hz.
(b) 500 Hz-1 kHz.
(c) 2 kHz-5 kHz.
(d) 20 kHz-50 kHz.
Answer : (c) 2 kHz-5 kHz.
270. Which one of the following is correct ?
The convention is that the number 0 has the normal form representation as
(a) 0
(b) .0
(c) 0.0
(d) 0.10°
Answer : (c) 0.0
271. A number is expressed in binary two’s complement as 10011. Its decimal equivalent value is
(a) 19
(b) 13
(c) -19
(d) -13
Answer : (d) -13
272. An 8085 microprocessor executes the following instructions:
Two numbers are represented in signed 2’s complement form as P = 11101101 and Q = 11100110
If Q is subtracted from P, the value obtained in signed 2’s complement form is
(a) 100000111
(b) 00000111
(c) 11111001
(d) 011111001
Answer : (b) 00000111
273. The two numbers represented in signed 2’s complement form are P = 11101101 and Q = 11100110. If Q is subtracted from P, the value obtained in signed 2’s complement form is
(a) 100000111
(b) 00000111
(c) 11111001
(d) 111111001
Answer : (b) 00000111
274. Decimal number +52 and -52 are
(a) 0110100 and 1110100
(b) 0101011 and 1101011
(c) 0110100 and 1101011
(d) None of these.
Answer : (a) 0110100 and 1110100
275. What is the octal equivalent of decimal 0.3125?
(a) 0.42
(b) 0.3125
(c) 0.24
(d) 0.12
Answer : (a) 0.42
276. The binary equivalent of hexadecimal number 4F2D is
(a) 0101 1111 0010 1100
(b) 0100 1111 0010 1100
(c) 0100 1110 0010 1101
(d) 0100 1111 0010 1101
Answer : (d) 0100 1111 0010 1101