Analog CMOS Integrated Circuit Design Current Mirrors Jawdat

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Analog CMOS Integrated. Circuit Design Current Mirrors Jawdat Abu-Taha Department of Electrical and Computer

Analog CMOS Integrated. Circuit Design Current Mirrors Jawdat Abu-Taha Department of Electrical and Computer Engineering Islamic University of Gaza jtaha@iugaza. edu. ps 1

Applications of Current Sources 2

Applications of Current Sources 2

Simple Resistive Biasing for Current Source 3

Simple Resistive Biasing for Current Source 3

Problems • Output current depends on: – Supply – Process – Temperature • What

Problems • Output current depends on: – Supply – Process – Temperature • What if the bias voltage is independent of supply voltage? • Is there a way of generating reliable currents? 4

Basic Idea Typically we assume that one precisely defined current source is available and

Basic Idea Typically we assume that one precisely defined current source is available and other current sources copy their current from this precise source. Iout is a function of gate-source voltage 5

Basic Idea This structure is called current mirror 6

Basic Idea This structure is called current mirror 6

Question • What happens if the two transistors in the basic current mirror have

Question • What happens if the two transistors in the basic current mirror have different sizes? 7

Example Assuming all the transistors are in saturation region, find Iout: 8

Example Assuming all the transistors are in saturation region, find Iout: 8

Current Mirrors: Amplifier Bias Example 9

Current Mirrors: Amplifier Bias Example 9

Current Mirrors: Signal Amplification Example • Find the small signal voltage gain of the

Current Mirrors: Signal Amplification Example • Find the small signal voltage gain of the following circuit. 11

Effect of Channel Length Modulation 12

Effect of Channel Length Modulation 12

Cascode Current Mirror 13

Cascode Current Mirror 13

Cascode Current Mirror 15

Cascode Current Mirror 15

Cascode Current Mirror SM EECE 488 Set 5 - Current Mirrors 16

Cascode Current Mirror SM EECE 488 Set 5 - Current Mirrors 16

Cascode Current Mirror 17

Cascode Current Mirror 17

Cascode Current Mirror Biasing 19

Cascode Current Mirror Biasing 19

Cascode Current Mirror Biasing 20

Cascode Current Mirror Biasing 20

Current Mirror Biasing 21

Current Mirror Biasing 21

Basic Circuit to Generate Supply Independent Current 22

Basic Circuit to Generate Supply Independent Current 22

Supply Independent Current 23

Supply Independent Current 23

Supply Independent Current 25

Supply Independent Current 25

Start-up Problem 26

Start-up Problem 26

Start-up Problem 27

Start-up Problem 27

Active Current Mirrors 29

Active Current Mirrors 29

Active Current Mirrors in Differential to Single-Ended Amplifiers 30

Active Current Mirrors in Differential to Single-Ended Amplifiers 30

Differential to Single-Ended Amplifiers 31

Differential to Single-Ended Amplifiers 31

Calculation of Gm 32

Calculation of Gm 32

Small-Signal Gain 33

Small-Signal Gain 33

Common Mode Characteristics 34

Common Mode Characteristics 34

Common Mode 35

Common Mode 35

Common Mode 36

Common Mode 36