Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Like this presentation? Why not share!

No Downloads

Total views

24,013

On SlideShare

0

From Embeds

0

Number of Embeds

4

Shares

0

Downloads

0

Comments

0

Likes

8

No embeds

No notes for slide

- 1. Cascode AmplifierModule Title: Analog and mixed signal circuit design Date: 2nd July 2012 M. S. Ramaiah School of Advanced Studies 1
- 2. Contents• Introduction• Cascode amplifier• Small signal model• Gain calculation• Cascode Current mirror• Cascode differential amplifier• Conclusion• References M. S. Ramaiah School of Advanced Studies 2
- 3. Multi-Stage Amplifiers (Cascading)• We can cascade different types of amplifiers to get desired overall characteristics. Often want: – High input impedance – High gain – Low output impedance – Higher gain• Mix and match cascades of different types of amplifiers to get desired result M. S. Ramaiah School of Advanced Studies 3
- 4. Introduction• Constructed using two transistors, one operating as CS and the other as a CG• Best of both the circuit configurations namely, – Moderate input impedance and high voltage gain of CS configuration – Very large output impedance, large output voltage swing and much larger band width of CG configuration.• Disadvantage: Requires two transistors and a relatively high supply voltage.• Applications: Used in current mirrors to increase output impedance, as a modulator for amplitude modulation, M. S. Ramaiah School of Advanced Studies 4
- 5. Comparison of CSA with a Cascode amp RL=300k D G M1VGS1=0.6V S 5u/0.35u vout vin Figure 1. Common source amplifier [Sharma 2010] Figure 2. Cascode amplifier [Sharma 2010] M. S. Ramaiah School of Advanced Studies 5
- 6. Cascode amplifierFigure 3. Cascode amplifier [Sharma 2010] M. S. Ramaiah School of Advanced Studies 6
- 7. Waveforms for Cascode amplifier for varying load Figure 4. Waveforms for change of output with respect to load M. S. Ramaiah School of Advanced Studies 7
- 8. Small signal modelFigure 5. Small signal model of cascode amplifier [Sharma 2010] M. S. Ramaiah School of Advanced Studies 8
- 9. Gain calculationFigure 6. Gain calculation [Sharma 2010] M. S. Ramaiah School of Advanced Studies 9
- 10. Cascode Current Mirror • This circuit does not need an external voltage bias. • The reference side of the mirror generates the bias voltages for both the transistors of the cascode output side. • However, this reduces the voltage range over which the output may swing.Figure 7. (a) Current mirror (b) Cascode current mirror (c) Simulation waveforms [Sharma 2010] M. S. Ramaiah School of Advanced Studies 10
- 11. Common-Source - Source-Follower Cascade RD M2 Rs M1 vO Cout vS IS1 CS IS2 RLD Figure 8. Common source and source follower cascode [Sharma 2010] M. S. Ramaiah School of Advanced Studies 11
- 12. Cascode Differential amplifier• Use of cascoding to increase load resistance• Cascode both the active loads and the differential pair – Higher effective load resistance – Higher ro for the differential pair – Reduces Miller effect M7 M8 M5 M6 vo Vbias M3 M4 M1 M2 vid I Figure 9. Cascode differential amplifier [Baker 2010] M. S. Ramaiah School of Advanced Studies 12
- 13. Summary• Best of both the circuit configurations (common source and common gate)• The cascode arrangement offers high gain, high stability and high input impedance• Wide applications as in current mirrors, modulators and differential OpAmp M. S. Ramaiah School of Advanced Studies 13
- 14. References• Dinesh Sharma (2010) CMOS Mixed Signal Design: OpAmp Design [online] available from < www.ee.iitb.ac.in/~smdp/DKStutorials/ opamp-tutorial.pdf > [01st July 2012]• Jacob Baker, R. (2010) CMOS: Circuit Design, Layout and Simulation. 3rd edn. Wiley-IEEE• Phillip E. Allen., and Douglas R, Holberg. (2002) CMOS Analog Circuit Design. 2nd edn. Oxford University Press M. S. Ramaiah School of Advanced Studies 14

No public clipboards found for this slide

×
### Save the most important slides with Clipping

Clipping is a handy way to collect and organize the most important slides from a presentation. You can keep your great finds in clipboards organized around topics.

Be the first to comment