224 ◆ B J T

CIRCUIT-ACTION QUIZ Answers can be found at www.pearsonglobaleditions.com/Floyd.

1. If a transistor with a higher bDC is used in Figure 4–9, the collector current will
(a) increase (b) decrease (c) not change
2. If a transistor with a higher bDC is used in Figure 4–9, the emitter current will
(a) increase (b) decrease (c) not change
3. If a transistor with a higher bDC is used in Figure 4–9, the base current will
(a) increase (b) decrease (c) not change
4. If VBB is reduced in Figure 4–16, the collector current will
(a) increase (b) decrease (c) not change
5. If VCC in Figure 4–16 is increased, the base current will
(a) increase (b) decrease (c) not change
6. If the amplitude of Vin in Figure 4–22 is decreased, the ac output voltage amplitude will
(a) increase (b) decrease (c) not change
7. If the transistor in Figure 4–24 is saturated and the base current is increased, the collector
current will
(a) increase (b) decrease (c) not change
8. If RC in Figure 4–24 is reduced in value, the value of IC(sat) will
(a) increase (b) decrease (c) not change
9. If the transistor in Figure 4–39 is open from collector to emitter, the voltage across RC will
(a) increase (b) decrease (c) not change
10. If the transistor in Figure 4–39 is open from collector to emitter, the collector voltage will
(a) increase (b) decrease (c) not change
11. If the base resistor in Figure 4–39 is open, the transistor collector voltage will
(a) increase (b) decrease (c) not change
12. If the emitter in Figure 4–39 becomes disconnected from ground, the collector voltage will
(a) increase (b) decrease (c) not change

SELF-TEST Answers can be found at www.pearsonglobaleditions.com/Floyd.

Section 4–1 1. The term bipolar refers to the use of
(a) holes (b) electrons (c) holes and electrons (d) neither (a), (b), nor (c)
2. In an npn transistor, the n regions are
(a) base and emitter (b) base and collector (c) emitter and collector (d) base
Section 4–2 3. For operation as an amplifier, the base of an npn transistor must be
(a) positive with respect to the emitter
(b) negative with respect to the emitter
(c) positive with respect to the collector
(d) 0 V
4. The emitter current is always
(a) greater than the base current
(b) less than the collector current
(c) greater than the collector current
(d) answers (a) and (c)
Section 4–3 5. The a of a transistor is its
(a) current gain (b) ratio of collector current to emitter current
(c) power gain (d) internal resistance
 S -T ◆ 225

6. If IC is 0.95 times larger than IE, then a is

(a) 0.05 (b) 1 (c) 0.95 (d) 1.05
7. The approximate voltage across the forward-biased base-emitter junction of a silicon BJT is
(a) 0 V (b) 0.7 V (c) 0.3 V (d) VBB
8. The bias condition for a transistor to be used as a linear amplifier is called
(a) forward-reverse (b) forward-forward
(c) reverse-reverse (d) collector bias
Section 4–4 9. If the output of a transistor amplifier is 15 V rms and the input is 200 mV rms, the voltage gain is
(a) 750 (b) 7.5 (c) 75 (d) 13.33
10. When a lowercase r9 is used in relation to a transistor, it refers to
(a) a low resistance (b) a wire resistance
(c) an internal ac resistance (d) a source resistance
11. In a given transistor amplifier, RC = 4.1 kV and r9e = 30 V, the voltage gain is approximately
(a) 7.32 (b) 136.67 (c) 0.0073 (d) 44
Section 4–5 12. When operated in cutoff and saturation, the transistor acts like a
(a) linear amplifier (b) switch
(c) variable capacitor (d) variable resistor
13. In cutoff, VCE is
(a) 0 V (b) minimum (c) maximum
(d) equal to VCC (e) answers (a) and (b) (f) answers (c) and (d)
14. In saturation, VCE is
(a) 0.7 V (b) equal to VCC (c) minimum (d) maximum
15. To saturate a BJT,
(a) IB = IC(sat) (b) IB 7 IC(sat)/bDC
(c) VCC must be at least 10 V (d) the emitter must be grounded
16. Once in saturation, a further increase in base current will
(a) cause the collector current to increase
(b) not affect the collector current
(c) cause the collector current to decrease
(d) turn the transistor off
Section 4–6 17. In a phototransistor, the base current is produced when
(a) light strikes a photosensitive semiconductor base region
(b) light strikes a photosensitive semiconductor collector region
(c) light strikes a photosensitive semiconductor emitter region
(d) neither (a), (b), nor (c)
18. A key parameter in optocouplers is the CTR, which is the
(a) current transfer rate (b) collector transfer rate
(c) current transfer ratio (d) neither (a), (b), nor (c)
19. An optocoupler usually consists of
(a) two LEDs (b) an LED and a photodiode
(c) an LED and a phototransistor (d) both (b) and (c)
Section 4–8 20. The term floating point refers to a point in the circuit
(a) not electrically connected to ground or a solid voltage
(b) not electrically connected to ground
(c) not electrically connected to a solid voltage
(d) neither (a), (b), nor (c)
21. A DMM measuring on open transistor junction shows
(a) 0 V (b) 0.7 V (c) OL (d) VCC