1. Electronic PRINCIPLES
MALVINO & BATES
Electronic
PRINCIPLES
SEVENTH EDITION

2. Chapter 11
CC and CB Amplifiers

3. Topics Covered in Chapter 11
CC amplifier
Output impedance
Cascading CE and CC
Darlington connection
Voltage regulation
CB amplifier

4. CC amplifier Known as an emitter follower
The collector is at ac ground
Stable voltage gain
High input impedance
Low distortion

5. The common-collector or emitter follower amplifier +VCC
ac ground
vout
vin R2 RE RL

6. T model of the emitter follower amplifier
re = RE RL re
re + re’
AV = R1 R2
re’
vin
vout = iere re
vin= ie(re + re’)

7. p model of the emitter follower amplifier
zin(stage) = R1 R2 b(re + re’) R1 R2
b(re + re’) re
vout
vin

8. The output side of a common-emitter amplifier
Applying Thevenin’s theorem: RC RL
vth RC RL
The output impedance is equal to RC.

9. T model of the emitter follower amplifier
Apply Thevenin’s theorem to point A:
vth
zout RL A RG R1 R2
re’ A RL RE

10. ( ) Output impedance of the emitter follower amplifier R1 R2 RG
re’ +
R1 R2 RG b ( )
zout = RE
The current gain of the amplifier steps down
the impedance of the base circuit. Thus, the
output impedance of this amplifier is small.

11. Common-collector buffer
A common-emitter (CE) stage with a low resistance load overloads with a small voltage gain
A common-collector (CC) stage placed between a CE stage and the load reduces overload and acts as a buffer

12. Darlington pair
Two transistors connected with the emitter of the first transistor connected to the base of the second transistor
The overall gain is equal to the product of the individual current gains

13. Darlington connection Darlington transistorQ1 Q2
b = b1b2
Darlington transistors are manufactured with transistors in one case

14. Zener follower A combination of a zener diode and an emitter follower
Provides a regulated output voltage with a large load current
The zener current is much smaller than the load current

15. Zener follower circuit
+VCC RL RS
Vout VZ
Vout = VZ - VBE
IB =
Iout
bdc
zout = re’ + RZ

16. Two-transistor voltage regulator
Two transistors and a zener diode
Uses an amplified feedback voltage to regulate the output voltage

17. Two-transistor
voltage regulator
R3 + R4 R4
(VZ + VBE)
Vout =
+Vin
Vout Q2 R2 R1 R3 RL Q1 R4 VZ

18. Common-base amplifier
The base is at ac ground
The input drives the emitter and the output is taken from the collector
No current gain but has a high voltage gain
Low input impedance
High output impedance
High frequency applications

19. CB amplifier circuit