31. Which of the following component is not used for audio frequency?
A. RC oscillator
B. Wein bridge oscillator
C. LC oscillator
D. None of the mentioned
Answer: C
RC and wein bridge oscillators are suitable for audio frequency range because the size of R and C components becomes very large for generating low frequencies.
32. If the resistor and capacitor values are the same in the Quadrature oscillator. Find its frequency of oscillation for R = 50 kΩ and C = 0.01µF.
A. 112Hz
B. 275Hz
C. 159Hz
D. 318Hz
Answer: D
Frequency of Quadrature oscillator
fo = 1/(2πRC.
= > fo = 1/(2π×50 kΩ×0.01µF) = 318Hz.
33. What is the possible method used in a Quadrature oscillator to remove distortion from the output waveform?
A. Replace the resistor at the input of a non-inverting type amplifier with a potentiometer
B. Replace the resistor at the output of a non-inverting type amplifier with a potentiometer
C. Replace the resistor at the input of inverting type amplifier with a potentiometer
D. None of the mentioned
Answer: A
The resistor at the input of a non-inverting type amplifier is replaced with a potentiometer to eliminate any possible distortion in the output waveform.
34. A Biphasic oscillator produces an output signal that has
A. Cosine wave only
B. Both sine and cosine wave
C. Two identical sine wave
D. Two identical cosine wave
Answer: C
A biphasic oscillator is a sine wave oscillator. Therefore, the output signals will be two identical sine waves that are 180o out of phase with each other.
35. If the output of the sinewave oscillator is Vsinωot, then determine the output of the inverter in the Biphasic oscillator.
A. Vsin(ωot+(3π/2))
B. Vsin(ωot+2π)
C. Vsin(ωot+π)
D. Vsin(ωot+(π/2)
Answer: B
Since the output of the Biphasic oscillator is 180o out of phase with each other. The sine wave passing through the inverting amplifier (with a gain of one) outputs the signal with a 180o phase shift.
36. A function generator can produce
A. Many identical waves
B. Square and sine waves only
C. Different types of waves simultaneously
D. None of the mentioned
Answer: C
Oscillator circuits generate only one type of waveform like square, triangular, or sine wave separately, whereas a function generator can produce all three types of waves simultaneously.
37. Which of the following have distorted sinewave?
A. Function generator
B. Biphasic oscillator
C. RC phase shift oscillator
D. Wein bridge oscillator
Answer: A
The sine shaper in the function generator produces a sine wave by rounding off the tips of the triangular wave. The distortion of the sine wave thus produced is very high compared to the sine waves generated by another oscillator.
38. Usually circuit producing sine waves are called as
A. Oscillators
B. Generators
C. Multivibrators
D. All of the mentioned
Answer: A
The generators and the oscillators are equivalent terms, they can be interchangeable. Therefore, the circuits producing sine waves are called oscillators, while those generating a square wave or triangular wave are generators.
39. An IC function generator can allow the signals for
A. Amplitude Modulation (AM)
B. Frequency Modulation (FM)
C. Frequency Shift Keying (FSK)
D. All of the mentioned
Answer: D
IC function generator allows FM, AM, and FSK of signals in addition to producing different waveforms with variable duty cycle pulse.
40. The current in the XR-2206 Function generator is determined by
A. External resistors
B. External capacitors
C. External capacitors or external resistors
D. Both external capacitor and external resistor
Answer: C
The constant current is determined by the external resistors connected to current switches or the external capacitor connected to the current-controlled oscillator.
41. What will be the output, if a 180Ω resistor that was connected between the 13th and 14th pin terminal is removed?
A. A triangular wave
B. A sine wave
C. A square wave
D. A rectangular wave
Answer: A
When pins 13 and 14 are open, the gain of the sine shaper becomes linear and the output from the sine shaper will be a triangular wave.
42. Find the difference of potential that can be applied to the XR-2206 function generator.
A. 26v
B. 5v
C. 19v
D. 30v
Answer: C
If the power is applied to both V+ and V– inputs. Then, the difference of potential (i.e. V+ – V–) should be at least +10v but less than 26v.
43. The value of current and frequency of the output waveform is 5A and 13.33kHz. Find the capacitance value in the function generator?
A. 250µF
B. 120µF
C. 850µF
D. 370µF
Answer: B
The frequency of the output waveform
f = (0.32×I)/C
= > C = (0.32×I)/f
= (0.32×5A./13.33kHz = 120µF.
44. How many sets of pins are required to control the frequency in the XR-2206 function generator?
A. Two
B. Three
C. Four
D. None of the mentioned
Answer: B
Frequency can be controlled by three sets of pin
1) Capacitor (100pF≤C≤100µF) connected to the current controlled oscillator
2) Resistor connected between the current switches
3) Voltage at Frequency Shift Keying connected to current switches.
45. How is the square wave output generated in op-amp?
A. Op-amp is forced to operate in the positive saturation region
B. Op-amp is forced to operate in the negative saturation region
C. Op-amp is forced to operate between positive and negative saturation region
D. None of the mentioned
Answer: C
Square wave outputs are generated where the op-amp is forced to operate in a saturated region, that is, the output of the op-amp is forced to swing repetitively between positive saturation, +Vsat, and negative saturation, -Vsat.
2. The following circuit represents a square wave generator. Determine its output voltage
A. -13 v
B. +13 v
C. ± 13 v
D. None of the mentioned
Answer: A
The differential output voltage
Vid = Vin1 – Vin2 = 3-7v = -4v.
The output of the op-amp in this circuit depends on the polarity of
differential voltage V0 = -Vsat ≅ -Vee = -13 v.
46. Determine the expression for time period of a square wave generator
A. T = 2RC ln×[( R1+ R2) / ( R2)].
B. T = 2RC ln×[( 2R1+ R2) / ( R2)].
C. T = 2RC ln×[( R1+ 2R2) / ( R2)].
D. T = 2RC ln×[( R1+ R2) / (2 R2)].
Answer: B
The time period of the output waveform for a square wave generator is
T = 2RC ln×[(2R1+ R2)/( R2)].
47. What will be the frequency of the output waveform of a square wave generator if R2 = 1.16 R1?
A. fo = (1/2RC)
B. fo = (ln/2RC)
C. fo = (ln /2 ×√RC)
D. fo = (ln/√(2 RC.)
Answer: B
When R2 = 1.16 R1,
fo = 1/2RC× ln[ (2R1+ R2) / R2]
= 1/2RC ×ln [(2R1 + 1.161R1 )/ (1.161R1)]
= 1/( 2RC×ln2.700) = 1/2RC.
6. What could be the possible output waveform for a free-running multivibrator whose op-amp has a supply voltage of ±5v operating at 5khz?
Answer: C
In a free-running multivibrator, the output is forced to swing repetitively between positive and negative saturation to produce a square wave output.
49. The value of series resistance in the square wave generator should be 100 kΩ or higher to
A. Prevent excessive differential current flow
B. Increase resistivity of the circuit
C. Reduce output offset voltage
D. All of the mentioned
Answer: A
In practice, each inverting and non-inverting terminal needs a series of resistance to prevent excessive differential current flow because the inputs of the op-amp are subjected to large differential voltages.
50. Why Zener diode is used at the output terminal of the square wave generator?
A. To reduce both output and capacitor voltage swing
B. To reduce output voltage swing
C. To reduce input voltage swing
D. To reduce capacitor voltage swing
Answer: B
A reduced peak-peak output voltage swing can be obtained in the square wave generator by using back-to-back Zener diodes at the output terminal.
