Bipolar Junction Triodes (BJTs) topics include: The basics of BJT, device structures and physical operations, circuits, current-voltage properties, amplifier design, signal operations and circuit configuration and biasing. A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device that can amplify signals. It's a current-controlled device that consists of two p-n junctions, a common region called the base, and two outer regions called the emitter and collector.  BJTs are known as bipolar transistors because they involve the operation of charge carriers of both polarities.... Show more

Bipolar Junction Triodes (BJTs) topics include: The basics of BJT, device structures and physical operations, circuits, current-voltage properties, amplifier design, signal operations and circuit configuration and biasing.

A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device that can amplify signals. It's a current-controlled device that consists of two p-n junctions, a common region called the base, and two outer regions called the emitter and collector. 

BJTs are known as bipolar transistors because they involve the operation of charge carriers of both polarities. They can function as current regulators by allowing a small current to control a larger current. 
BJTs can consist of either a P-N-P or an N-P-N semiconductor “sandwich” structure. In a PNP transistor, the regions are, respectively, p type, n type, and p type. In an NPN transistor, the regions are n type, p type, and n type. 

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Electronic Devices and Circuits Practice Test: Bipolar Junction Triodes (BJTs)

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25 Questions

1. For Vcc = 15V, R1 = 100 kΩ, R(E) = 3.9 kΩ, R(C) = 6.8 kΩ and ß = 100, determine the dc collector voltage for each transistor in the figure shown below.

8.5 V4.25 V17 V12.75 V

2. Which of the following is true for a pnp transistor in active region?

CB junction is reversed bias and the EB junction is reverse biasCB junction is forward bias and the EB junction is reverse biasCB junction is forward bias and the EB junction is forward biasCB junction is reversed bias and the EB junction is forward bias

3. The circuit shown below is a small sine wave signal with average zero and transistor ß. Find R(C) to establish a dc collector voltage of about +5V.

20 kΩ5 kΩ10 kΩ15 kΩ

4. For the BJT to operate in active mode Collector-Base junction must be

Must reversed biasHeavily dopedLightly dopedMust be forward bias

5. Find R (in 2) from the following figure.

17.3 kΩ2.4 kΩ4.8 kΩ34.6 kΩ

6. A designer wishes to create a BJT amplifier with a gm of 50 mA/V and a base input resistance of 2000 O or more. What is the minimum ß he can tolerate for the transistor used?

150100250200

7. Which of the following is true for a pnp transistor in saturation region?

CB junction is reversed bias and the EB junction is reverse biasCB junction is forward bias and the EB junction is forward biasCB junction is reversed bias and the EB junction is forward biasCB junction is forward bias and the EB junction is reverse bias

8. The SI units of transconductance is

SiemensVolt/ ampereOhmAmpere/ volt

9. For Rl = 2 kΩ find Vo/Vb2 from the following figure.

-59.3 V/V-29.7 V/V-89.1 V/VNone of these

10. In cut off mode

The base-emitter junction is forward biased and emitter-collector junction is reversed biasedThe base-emitter junction is forward biased and emitter-collector junction is forward biasedThe base-emitter junction is reversed biased and emitter-collector junction is forward biasedThe base-emitter junction is reversed biased and emitter-collector junction is reversed biased

11. Which of the following represents the correct mathematical form of the term denoted by the symbol Rp?

All of the mentionedNone of theseß/gmVt/Ib

12. The collector current Ic is related to the emitter current Ie by a factor k. If b is the transistor parameter then the value of k in terms of b is

k = b/(b + 1)b = (k + 1)/kk = (b + 1)/bNone of these

13. For the amplifier circuit in the below figure with Vcc = +10 V, Rc = 1 kΩ and the DC collector bias current equal to Ic. The maximum possible negative output signal swing as determined by the need to keep the transistor in the active region.

10 IcIc0.1 Ic100 Ic

14. The correct relation between the emitter current Ie and the base current Ib is given by

Ie = (1 – ß) IbIb = (1 + α) IeIe = (1 + ß) IbIb = (α – 1) Ie

15. The circuit shown below is a small sine wave signal with average zero and transistor ß. Find the value of R(E) to establish a dc emitter current of about 0.5 mA.

228.16 kΩ28.57 kΩ57.04 kΩ114.08 kΩ

16. The potential difference between the base and the collector Vcb in a pnp transistor in saturation region is ________

0.5 V-0.5V-0.2 V0.2 V

17. Twelve 6 ohm resistors are used to form an edge of a cube. The resistance between two diagonally opposite corner of the cube (in ohm) is ________

6/5565/6

18. A pseudo-noise (PN) sequence is generated using a feedback shift register of length m = 4. The chip rate is 107 chips per second. What is the PN sequence length?

18101215

19. A pseudo-noise (PN) sequence is generated using a feedback shift register of length m = 4. The chip rate is 107 chips per second. The chip duration will be?

1 ms1µs0.1 µs0.1 ms

20. The number of pn junctions in a BJT is/are

2413

21. For the amplifier circuit in the below figure with Vcc = +10 V, Rc = 1 kΩ and the DC collector bias current equal to Ic. Find the voltage gain.

200 Ic800 Ic100 Ic400 Ic

22. An amplifier is measured to have an internal resistance of 10 kΩ, voltage gain of 100V/V and output resistance of 100 Ω. Also, when a load resistance of 1 kΩ is connected between the output resistance if found to decrease to 8 kΩ. If the amplifier is fed with the signal source having an internal resistance of 2 kΩ. Find Ai.

182 A/A728 A/A546 A/A364 A/A

23. A transistor operating with nominal gm of 60 mA/V has a ß that ranges from 50 to 200. Also, the bias circuit, being less than ideal, allows a 20% variation in Ic. What is the largest value found of the resistance looking into the base?

1050 ohm3150 ohm4200 ohm21000 ohm

24. A lightning bolt carrying 15,000 A lasts for 100 s. If the lightning strikes an airplane flying at 2 km, the charge deposited on the plane is _________

1.5 C1500 C75 C13.33 C

25. A transistor with ß = 120 is biased to operate at a dc collector current of 1.2 mA. Find the value of Re.

20.6 ohm2.5 ohm25.2 ohm30.4 ohm