1 / 26

ECE 442 Solid-State Devices & Circuits 12. Frequency Response of CS Amplifiers

ECE 442 Solid-State Devices & Circuits 12. Frequency Response of CS Amplifiers. Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois jschutt@emlab.uiuc.edu. MOSFET - Gate Capacitance Effect. Triode region :. Saturation region :. Cutoff :.

dylan
Télécharger la présentation

ECE 442 Solid-State Devices & Circuits 12. Frequency Response of CS Amplifiers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ECE 442 Solid-State Devices & Circuits 12. Frequency Response of CS Amplifiers Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois jschutt@emlab.uiuc.edu

  2. MOSFET - Gate Capacitance Effect Trioderegion: Saturation region: Cutoff:

  3. MOSFET – Junction Capacitances Overlap capacitance (gate-to-source):

  4. MOSFET High-Frequency Model

  5. CS - Three Frequency Bands

  6. Unity-Gain Frequency fT fT is defined as the frequency at which the short-circuit current gain of the common source configuration becomes unity Define: (neglect sCgdVgs since Cgdis small)

  7. Calculating fT For s=jw, magnitude of current gain becomes unity at fT~ 100 MHz for 5-mm CMOS, fT~ several GHz for 0.13mm CMOS

  8. CS - High-Frequency Response

  9. CS - High-Frequency Response

  10. CS - High-Frequency Response

  11. CS – Miller Effect Define Ceq such that

  12. CS – Miller Effect fo is the corner frequency of the STC circuit

  13. CS – Miller Effect

  14. Example Rsig = 100 kW, RG=4.7 MW, RD =15 kW, gm=1mA/V, rds=150 kW, RL=10 kW, Cgs=1 pF and Cgd=0.4 pF

  15. Example (cont’) Upper 3 dB frequency is at:

  16. BJT Capacitances Base: Diffusion Capacitance: Cde (small signal) where Qn is minority carrier charge in base where tF is the forward transit time (time spent crossing base)

  17. BJT Capacitances Base-emitter junction capacitance: Cjeo is Cje at 0 V. Voe is EBJ built in voltage ~ 0.9 V

  18. BJT Capacitances In hybrid pi model, Cde+Cje=Cp Collector-base junction capacitance Cmois Cm at 0 V. Voc is CBJ built in voltage ~ 0.9 V Cp is around a few tens of pF Cm is around a few pF

  19. High-Frequency Hybrid-p Model

  20. CE - Three Frequency Bands

  21. CS – Miller Effect – Exact Analysis

  22. CS – Miller Effect – Exact Analysis

  23. CS – Miller Effect – Exact Analysis We neglect the terms in s2since Miller If we multiply through by

  24. CS – Miller Effect – Exact Analysis From which we extract the 3-dB frequency point

  25. CS – Miller Effect – Exact Analysis If Gg is negligible IfRi =0

  26. Example For the discrete common-source MOSFET amplifier shown, the transistor has VT= 1V, mCox(W/L) = 0.25 mA/V2, l = 0, Cgs= 3 pF, Cgd= 2.7 pF and VA= 20 V. Assume that the coupling capacitors are short circuits at midband and high frequencies. • Find the 3dB bandwidth if Ri=0 • (b) Find the 3dB bandwidth if Ri= 10 kW

More Related