58 + Mcqs in PNPN Page 1 McqOptions

1.	For an SCS, a ________ pulse at the anode gate turns the device on, while a ________ pulse will turn it off.
A.	negative, positive
B.	positive, negative
Answer» B. positive, negative

Discussion

2.	The minimum operating voltage of the UJT is typically ________ that of a similarly rated PUT.
A.	lower than
B.	the same as
C.	higher than
D.	None of the above
Answer» D. None of the above

Discussion

3.	In a programmable unijunction transistor (PUT), the ________ can be controlled through a couple of resistors and the supply voltage.
A.	interbase resistance RBB
B.	intrinsic stand-off ratio
C.	emitter firing potential VP
D.	All of the above
Answer» E.

Discussion

4.	The peak and valley currents of the PUT are typically ________ those of a similarly rated UJT.
A.	lower than
B.	the same as
C.	higher than
D.	None of the above
Answer» B. the same as

Discussion

5.	An opto-isolator contains ________.
A.	an infrared LED
B.	a photodetector
C.	both an infrared LED and a photodetector
D.	None of the above
Answer» D. None of the above

Discussion

6.	________ is(are) example(s) of applications of phototransistors.
A.	Punch-card readers
B.	Lighting control (for example, on highways)
C.	Level indication
D.	All of the above
Answer» E.

Discussion

7.	The switching time of an opto-isolator ________ with increased current, while for many devices it is exactly the reverse.
A.	increases
B.	decreases
C.	remains the same
D.	None of the above
Answer» C. remains the same

Discussion

8.	________ in light intensity corresponds with ________ in collector current.
A.	An increase, an increase
B.	An increase, a decrease
C.	A decrease, an increase
D.	None of the above
Answer» B. An increase, a decrease

Discussion

9.	The current induced by photoelectric effects is the ________ current of the transistor.
A.	collector
B.	base
C.	emitter
D.	None of the above
Answer» C. emitter

Discussion

10.	________ is (are) the element(s) of a unijunction transistor's equivalent circuit.
A.	One fixed resistor
B.	A variable resistor
C.	A diode
D.	All of the above
Answer» E.

Discussion

11.	In general, the triggering (turn-on) anode gate current is ________ the required cathode gate current.
A.	larger than
B.	the same as
C.	smaller than
D.	None of the above
Answer» B. the same as

Discussion

12.	A(n) ________ can be triggered in either direction.
A.	SCR
B.	Shockley diode
C.	diac
D.	SCS
Answer» D. SCS

Discussion

13.	To turn on an SCS device, a ________ pulse must be applied to the anode gate terminal; to turn off the device, a ________ pulse is required.
A.	positive, positive
B.	negative, positive
C.	positive, negative
D.	negative, negative
Answer» C. positive, negative

Discussion

14.	The anode gate connection can be used to turn the SCS device ________.
A.	on
B.	off
C.	neither on nor off
D.	either on or off
Answer» E.

Discussion

15.	The ________ the anode gate current, the ________ the required anode-to-cathode voltage to turn the SCS device on.
A.	higher, higher
B.	lower, lower
C.	higher, lower
D.	None of the above
Answer» D. None of the above

Discussion

16.	In a half-wave variable-resistance phase control operation, the control cannot be extended past a ________ phase displacement.
A.	45º
B.	90º
C.	135º
D.	180º
Answer» C. 135º

Discussion

17.	The ________ are the terminals of an SCS.
A.	anode, anode gate, cathode gate, and cathode
B.	anode, cathode, cathode gate, and gate
C.	anode, anode gate, cathode, and gate
D.	anode, cathode, and gate
Answer» B. anode, cathode, cathode gate, and gate

Discussion

18.	At –65ºC the minimum current that will trigger the series of an SCR is ________, while at +150ºC only ________ is required.
A.	20 mA, 100 mA
B.	50 mA, 75 mA
C.	75 mA, 50 mA
D.	100 mA, 20 mA
Answer» E.

Discussion

19.	The method(s) for turning off an SCR is (are) categorized as ________.
A.	current interruption
B.	forced commutation
C.	both current interruption and forced commutation
D.	None of the above
Answer» D. None of the above

Discussion

20.	The SCRs have typical turn-on times of ________ in the regeneration action.
A.	0.1 μs to 1 μs
B.	0.1 ms to 1 ms
C.	3 ms to 5 ms
D.	5 ms to 9 ms
Answer» B. 0.1 ms to 1 ms

Discussion

21.	In the conduction region, the dynamic resistance of the SCR is typically ________ to ________.
A.	0.01 , 0.1
B.	1 , 10
C.	50 , 100
D.	500 , 10 k
Answer» B. 1 , 10

Discussion

22.	________ are areas of application for SCRs.
A.	Relay controls
B.	Time-delay circuits
C.	Motor controls
D.	All of the above
Answer» E.

Discussion

23.	SCRs have been designed to control powers as high as ________, with individual ratings as high as ________ at ________.
A.	1800 MW, 10 A, 2000 V
B.	1800 MW, 2000 A, 10 V
C.	10 MW, 2000 A, 1800 V
D.	2000 MW, 10 A, 1800 V
Answer» D. 2000 MW, 10 A, 1800 V

Discussion

24.	The ________ are the terminals of SCRs.
A.	anode and cathode
B.	anode, gate, and cathode
C.	base, anode, and cathode
D.	gate and anode
Answer» C. base, anode, and cathode

Discussion

25.	The four-layer devices with a control mechanism are commonly referred to as ________.
A.	thyristors
B.	transistors
C.	diodes
D.	None of the above
Answer» B. transistors

Discussion

26.	The two-layer semiconductor diode has led to ________layer devices.
A.	three-
B.	four-
C.	five-
D.	All of the above
Answer» E.

Discussion

27.	Determine RB1 for a silicon PUT if it is determined that h = 0.84, VP = 11.2 V, and RB2 = 5 k.
A.	12.65 k
B.	16.25 k
C.	20.00 k
D.	26.25 k
Answer» E.

Discussion

28.	Which of the following devices has nearly the same turn-on time as turn-off time?
A.	SCR
B.	GTO
C.	SCS
D.	LASCR
Answer» C. SCS

Discussion

29.	How many layers of semiconductor materials does a silicon-controlled rectifier (SCR) have?
A.	2
B.	3
C.	4
D.	5
Answer» D. 5

Discussion

30.	A thyristor is a ________-layer semiconductor material device.
A.	2
B.	3
C.	4
D.	5
Answer» D. 5

Discussion

31.	Which of the following transistors is an SCR composed of?
A.	npn, pnp
B.	npn, npn
C.	pnp, pnp
D.	None of the above
Answer» B. npn, npn

Discussion

32.	This symbol is an example of a(n)________.
A.	SCR
B.	SCS
C.	GTO
D.	DIAC
Answer» C. GTO

Discussion

33.	Which of the following is (are) the advantages of the SCS over a corresponding SCR?
A.	Reduced turn-off time
B.	Increased control and triggering sensitivity
C.	More predictable firing situation
D.	All of the above
Answer» E.

Discussion

34.	Determine R B1 for a silicon PUT if it is determined that h = 0.84, V P = 11.2 V, and R B2 = 5 k .
A.	12.65 k
B.	16.25 k
C.	20.00 k
D.	26.25 k
Answer» E.

Discussion

35.	What is the typical range of turn-off times for SCRs?
A.	5 s to 30 s
B.	1 s to 5 s
C.	0.1 s to 1 s
D.	0.01 s to 0.1 s
Answer» B. 1 s to 5 s

Discussion

36.	What is the typical value of the triggering anode gate for SCS devices?
A.	1.5 mA
B.	150 A
C.	15 A
D.	1 A
Answer» B. 150 A

Discussion

37.	How many terminals does a silicon-controlled switch (SCS) device have?
A.	2
B.	3
C.	4
D.	5
Answer» D. 5

Discussion

38.	Which of the following areas is (are) applications of an SCS?
A.	Counters
B.	Pulse generators
C.	Voltage sensors
D.	All of the above
Answer» E.

Discussion

39.	What is the maximum current (rms) rating for commercially available LASCRs today?
A.	3 A
B.	15 A
C.	20 A
D.	25 A
Answer» B. 15 A

Discussion

40.	Which of the following parameters are usually provided by the manufacturer on the specification sheet for SCRs?
A.	Turn-on time (t on )
B.	Turn-off time (t off )
C.	Junction and case temperatures (t j and t c )
D.	All of the above
Answer» E.

Discussion

41.	Which of the following devices has (have) four layers of semiconductor materials?
A.	Silicon-controlled switch (SCS)
B.	Gate turn-off switch (GTO)
C.	Light-activated silicon-controlled rectifier (LASCR)
D.	All of the above
Answer» E.

Discussion

42.	This is an example of a high-isolation ________ gate.
A.	OR
B.	NOT
C.	AND
D.	NAND
Answer» D. NAND

Discussion

43.	An advantage of the SCR over the SCS is the reduced turn-off time.
A.	True
B.	False
C.	-
D.	-
Answer» C. -

Discussion

44.	Which of the transistors of an SCR are conducting when the SCR is fired and is in the conduction mode?
A.	npn
B.	pnp
C.	Both npn and pnp
D.	Neither npn nor pnp
Answer» D. Neither npn nor pnp

Discussion

45.	This symbol is an example of a(n) ________.
A.	SCR
B.	SCS
C.	GTO
D.	diac
Answer» D. diac

Discussion

46.	What is the frequency range of application of SCRs?
A.	About 10 kHz
B.	About 50 kHz
C.	About 250 kHz
D.	About 1 mHz
Answer» C. About 250 kHz

Discussion

47.	What is the range of the turn-on times in high-power SCR devices?
A.	30 s to 100 s
B.	10 s to 25 s
C.	5 s to 8 s
D.	1 s to 5 s
Answer» C. 5 s to 8 s

Discussion

48.	What is the range of the variable resistor in the equivalent circuit of a unijunction transistor?
A.	50 to 5 k
B.	6 k to 10 k
C.	5 to 50
D.	1 to 5
Answer» B. 6 k to 10 k

Discussion

49.	Which one of the SCR terminals fires the SCR?
A.	Anode
B.	Cathode
C.	Gate
D.	All of the above
Answer» D. All of the above

Discussion

50.	Which of the following devices has the smallest turn-off time?
A.	SCR
B.	GTO
C.	SCS
D.	LASCR
Answer» C. SCS

Discussion

Explore topic-wise MCQs in Active Filter Circuits.

For an SCS, a ________ pulse at the anode gate turns the device on, while a ________ pulse will turn it off.

The minimum operating voltage of the UJT is typically ________ that of a similarly rated PUT.

In a programmable unijunction transistor (PUT), the ________ can be controlled through a couple of resistors and the supply voltage.

The peak and valley currents of the PUT are typically ________ those of a similarly rated UJT.

An opto-isolator contains ________.

________ is(are) example(s) of applications of phototransistors.

The switching time of an opto-isolator ________ with increased current, while for many devices it is exactly the reverse.

________ in light intensity corresponds with ________ in collector current.

The current induced by photoelectric effects is the ________ current of the transistor.

________ is (are) the element(s) of a unijunction transistor's equivalent circuit.

In general, the triggering (turn-on) anode gate current is ________ the required cathode gate current.

A(n) ________ can be triggered in either direction.

To turn on an SCS device, a ________ pulse must be applied to the anode gate terminal; to turn off the device, a ________ pulse is required.

The anode gate connection can be used to turn the SCS device ________.

The ________ the anode gate current, the ________ the required anode-to-cathode voltage to turn the SCS device on.

In a half-wave variable-resistance phase control operation, the control cannot be extended past a ________ phase displacement.

The ________ are the terminals of an SCS.

At –65ºC the minimum current that will trigger the series of an SCR is ________, while at +150ºC only ________ is required.

The method(s) for turning off an SCR is (are) categorized as ________.

The SCRs have typical turn-on times of ________ in the regeneration action.

In the conduction region, the dynamic resistance of the SCR is typically ________ to ________.

________ are areas of application for SCRs.

SCRs have been designed to control powers as high as ________, with individual ratings as high as ________ at ________.

The ________ are the terminals of SCRs.

The four-layer devices with a control mechanism are commonly referred to as ________.

The two-layer semiconductor diode has led to ________layer devices.

Determine RB1 for a silicon PUT if it is determined that h = 0.84, VP = 11.2 V, and RB2 = 5 k.

Which of the following devices has nearly the same turn-on time as turn-off time?

How many layers of semiconductor materials does a silicon-controlled rectifier (SCR) have?

A thyristor is a ________-layer semiconductor material device.

Which of the following transistors is an SCR composed of?

This symbol is an example of a(n)________.

Which of the following is (are) the advantages of the SCS over a corresponding SCR?

Determine R B1 for a silicon PUT if it is determined that h = 0.84, V P = 11.2 V, and R B2 = 5 k .

What is the typical range of turn-off times for SCRs?

What is the typical value of the triggering anode gate for SCS devices?

How many terminals does a silicon-controlled switch (SCS) device have?

Which of the following areas is (are) applications of an SCS?

What is the maximum current (rms) rating for commercially available LASCRs today?

Which of the following parameters are usually provided by the manufacturer on the specification sheet for SCRs?

Which of the following devices has (have) four layers of semiconductor materials?

This is an example of a high-isolation ________ gate.

An advantage of the SCR over the SCS is the reduced turn-off time.

Which of the transistors of an SCR are conducting when the SCR is fired and is in the conduction mode?

This symbol is an example of a(n) ________.

What is the frequency range of application of SCRs?

What is the range of the turn-on times in high-power SCR devices?

What is the range of the variable resistor in the equivalent circuit of a unijunction transistor?

Which one of the SCR terminals fires the SCR?

Which of the following devices has the smallest turn-off time?

For an SCS, a pulse at the anode gate turns the device on, while a pulse will turn it off.

in light intensity corresponds with in collector current.

To turn on an SCS device, a pulse must be applied to the anode gate terminal; to turn off the device, a pulse is required.

The the anode gate current, the the required anode-to-cathode voltage to turn the SCS device on.

At –65ºC the minimum current that will trigger the series of an SCR is , while at +150ºC only is required.

In the conduction region, the dynamic resistance of the SCR is typically to .

SCRs have been designed to control powers as high as , with individual ratings as high as at .