0. Multistage Amplifiers
Two Stage CMOS OpAMP
Bipolar OpAmp
SPICE
March 3, 2005

1. HW #5
7.10, 7.21, 7.71, 7.88
Due Tuesday
March 3, 2005

2. Why Multistage?
Practical transistor amplifiers consist of a number of stages connected in cascade.
First stage typically high input impedance, & CMMR
Middle stages amplification
Last stage, low output impedance
March 3, 2005

3. Two stage CMOS
Q8,Q5:
current mirrors
March 3, 2005

4. Usually the leakage resistances are much larger than 1/g_m3
Differential Input
Usually the leakage resistances are much larger than 1/g_m3
March 3, 2005

5. Differential Gain
March 3, 2005

6. Differential Input
March 3, 2005

7. vG2=0, vG1=vid
March 3, 2005

8. Equivalent Circuit MOSFET Opamp
March 3, 2005

9. Bias Circuit for Opamp
Bias current independent of Supply Voltage and MOSFET threshold volage
Q_12, Q_13 deliberately mismatched, Q_12 4x wider
March 3, 2005

10. Bipolar Opamp
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11. Bipolar Opamp
March 3, 2005

12. Small Signal Analysis
Input and output Impedances
March 3, 2005

13. Gain of Second Stage
March 3, 2005

14. Last stage
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15. Small Signal Model
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16. Frequency Response
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17. Spice Simulation
March 3, 2005

18. Opamp Transfer Function
March 3, 2005

19. Differential Gain
March 3, 2005

20. Frequency Response Adjust frequency resonse by adding resistor in Q4
March 3, 2005

21. Common Mode Rejection Ratio
March 3, 2005