Topic 3 : Differential Amplifiers Using Half-Circuits

1. Part 2.2
Multi-Stage and
Differential Amplifiers
Assoc Prof Zheng Yuanjin email: yjzheng@ntu.edu.sg
EE2002 Analog Electronics

5. Bipolar Common-mode Half-Circuits
+VCC +VCC
+VCC +VCC
RC RC RC
R
C
R
C v
c1vC1 vC1v
C1 vC2
Q
1
Q
2
vev
IC vicvE
2REE
v
IC vIC 2REE
2R
EE
-VEE
(b) (c)2REE 2REE (a)
Q-point analysis
with no DC input
Large DC common-
mode input
Common-mode
signal analysis-VEE -VEE
All points on line of symmetry become open circuits.
• DC circuit with V set to zero is used to find amplifier’s Q-point.IC
• Half circuit (c) is used for common-mode signal analysis and represents
the C-E amplifier with emitter resistor 2R .EE
EE2002 Analog Electronics Multi-Stage and Differential Amplifiers 27

6. Multi-Stage and
Differential Amplifiers
-End of Lecture-