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

2. Applications of
Current
Sources 2

3. Simple
Resistive
Biasing
for
Current
Source 3

4. 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

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

6. Basic
Idea
This structure
is called current mirror 6

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

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

9. Current
Mirrors:
Amplifier Bias
Example 9

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

11. Effect of
Channel
Length
Modulation 12

12. Cascode
Current Mirror 13

13. Cascode
Current Mirror 15

14. Cascode
Current Mirror SM
EECE488 Set 5 - Current Mirrors 16

15. Cascode
Current Mirror 17

16. Cascode
Current
Mirror
Biasing 19

17. Cascode
Current
Mirror
Biasing 20

18. Current
Mirror
Biasing 21

19. Basic
Circuit to
Generate
Supply
Independent
Current 22

20. Supply
Independent
Current 23

21. Supply
Independent
Current 25

22. Start-up
Problem 26

23. Start-up
Problem 27

24. Active
Current
Mirrors 29

25. Mirrors in Differential Amplifiers to Single-Ended
Active
Current
Mirrors in Differential
Amplifiers to
Single-Ended 30

26. Differential to
Single-Ended
Amplifiers 31

27. Calculation of Gm 32

28. Small-Signal
Gain 33

29. Common
Mode
Characteristics 34

30. Common
Mode 35

31. Common Mode 36