FET lecture_ Electronics by Arif Sir
- 1. 1 EEE235 Field Effect Transistors (FET)-2
- 2. 2 EEE235 Typically L = 1 to 10 µm, W = 2 to 500 µm, and the thickness of the oxide layer is in the range of 0.02 to 0.1 µm. Field Effect (MOS) Transistor
- 3. 3 EEE235 The enhancement-type NMOS transistor with a positive voltage applied to the gate. An n channel is induced at the top of the substrate beneath the gate. Operation
- 4. 4 EEE235 vGS > Vt , small vDS applied.(0.1-0.2V) The channel conductance is proportional to vGS - Vt , and Drain current also proportional to (vGS - Vt) ; of course to vDS . Triode Region(applying a small vds)
- 5. 5 EEE235
- 6. 6 EEE235 Saturation Region (as vds increased)
- 7. 7 EEE235 Enhancement-type NMOS transistor operated with vGS > Vt . Drain current iD versus vDS
- 8. 8 EEE235 Derivation of the iD - vDS characteristic of the NMOS transistor.
- 9. 9 EEE235 Cross section of a CMOS integrated circuit. Note that the PMOS transistor is formed in a separate n- type region, known as an n well. Another arrangement is also possible in which an n-type body is used and the n device is formed in a p well.
- 10. 10 EEE235 •n-channel MOSFET in saturation, incorporating the output resistance ro . •The output resistance ro ≅ VA/ ID . Large-signal equivalent circuit model
- 11. 11 EEE235 The current-voltage characteristics of a depletion-type n-channel MOSFET for which Vt = -4 V and k’n (W/L) = 2 mA/V2 iD - vDS characteristics iD - vGS saturation
- 12. 12 EEE235 MOSFET as an amplifier.
- 13. 13 EEE235 Instantaneous voltages vGS and vD Small Signal
- 14. 14 EEE235 Models for MOSFET neglecting the dependence of iD on vDS in saturation (channel-length modulation effect)
- 15. 15 EEE235 Model with Output Resistance Including the effect of channel-length modulation modeled by output resistance ro = | VA |/ ID .
- 16. 16 EEE235 T model of the MOSFET augmented with the drain-to- source resistance ro. T model of the MOSFET
- 17. 17 EEE235 MOSFET current mirror. Sample Circuit Output characteristic of the current current mirror Q2 is matched to Q1 .
- 18. 18 EEE235 The CMOS common-source amplifier
- 19. 19 EEE235 The CMOS common-gate amplifier
- 20. 20 EEE235 (a) circuit; (b) small-signal equivalent circuit (c) simplified version of the equivalent circuit. The source follower