Lecture I: Introduction to pattern recognition

1
Differential and Multistage Amplifiers
2
Differential Amplifier

• Why Differential?

1. Much less sensitive to noise and interference
2. To bias and couple amplifier without the need of
   capacitors
3. Take advantage of the availability of large
   number of transistors at relatively low cost in IC

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3
The MOS Differential Pair

• Operation with a Common-Mode Input Voltage

4
Small-Signal Operation of the MOS Differential
Pair

• Differential Gain

single-ended output v.s. differential output
5
Small-Signal Operation of the MOS Differential
Pair

• Differential Gain (cont.)

Neglect ro
Virtual Ground, NO capacitor!
6
Small-Signal Operation of the MOS Differential
Pair

• Differential Gain Effect of ro

7
Small-Signal Operation of the MOS Differential
Pair

• Common-mode gain and common-mode rejection ration

Neglect ro
For single-end output
For differential output
8
Small-Signal Operation of the MOS Differential
Pair

• Common-mode gain and common-mode rejection
  ration
• Effect of RD Mismatch on CMRR

9
Small-Signal Operation of the MOS Differential
Pair

• Common-mode gain and common-mode rejection ration
• Effect of gm Mismatch on CMRR

neglecting ro
10
Frequency Response of the Differential Amplifier

• Analysis of the Resistively Loaded MOS Amplifier

Differential half-circuit Common Source
Amplifier
RSS Output Resistance of QS CSS Cdbs, Cgds,
Csb1, Csb2
11
Frequency Response of the Differential Amplifier
Analysis of the Resistively Loaded MOS Amplifier
(cont.)
12
Frequency Response of the Differential Amplifier
Analysis of the Resistively Loaded MOS Amplifier
(cont.)
Figure 7.37 Variation of (a) common-mode gain,
(b) differential gain, and (c) common-mode
rejection ratio with frequency.
13
Frequency Response of the Differential Amplifier
Analysis of the Active-Loaded MOS Amplifier
14
Frequency Response of the Differential Amplifier
Analysis of the Active-Loaded MOS Amplifier
(cont.)
Figure 7.39 The overall transconductance Gm as a
function of frequency.
15
Homework
7.1 (a, b), 7.2, 7.7, 7.9, 7.12, 7.14, 7.15