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EE314

Field Effect Transistors. Intel Pentium 4. Equivalent Circuits. EE314. MOSFET Transistor. Small-Signal Equivalent Circuits Examples Technology Future Devices. Chapter 12: Field Effect Transistors. -4. x 10. 6. VGS= 2.5 V. 5. Triode. Saturation. 4. VGS= 2.0 V. Quadratic

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EE314

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  1. Field Effect Transistors Intel Pentium 4 Equivalent Circuits EE314

  2. MOSFET Transistor • Small-Signal • Equivalent Circuits • Examples • Technology • Future Devices Chapter 12: Field Effect Transistors

  3. -4 x 10 6 VGS= 2.5 V 5 Triode Saturation 4 VGS= 2.0 V Quadratic Relationship (A) 3 VDS = VGS - VT D I 2 VGS= 1.5 V 1 VGS= 1.0 V 0 0 0.5 1 1.5 2 2.5 V (V) DS Current-Voltage RelationsMOSFET Transistor VDS = VGS - VT cut-off NMOS transistor, 0.25mm, Ld = 10mm, W/L = 1.5, VDD = 2.5V, VT = 0.4V

  4. Load-Line Analysis of NMOS Amplifier It is a graphical analysis similar to load-line analysis of pn diode. We look for the operating point Schematic Circuit Analysis: vGS vDS Input loop Output loop Load line

  5. Load-Line Analysis of NMOS Amplifier Exercise: Draw the Load line RD= 1 kW

  6. Load-Line Analysis of NMOS Amplifier Taking iD=0 or vDS=0 we find out the load lane and the quiescent operating point Q for VGS=4V Load line The quiescent values vin(t)=0 then iDQ=9 mA vGSQ=4V and vDSQ=11V Points A & B intersection of curve and the load-line for the maximum and the minimum gate voltage

  7. Load-Line Analysis of NMOS Amplifier (peak-to-peak amplitude is 2V) Input signal vDS(t) 12V peak-to-peak 2V peak-to-peak vin(t) Inverse operation The positive peak of the input occurs at the same time as the min. value of vDS. The output is not a symmetrical sinusoid! (nonlinear distortion)

  8. + vG _ Input Output Self Bias Circuits Analysis of amplifier circuits is often undertaken in two steps: (1) The dc circuit analysis to determine the Q point. It involves the nonlinear equation or the load-line method. This is called bias analysis The fixed-plus self-bias circuit Exercise: Find VG voltage as a function of VDD, R1 and R2

  9. + vG _ Input Output Self Bias Circuits Analysis of amplifier circuits is often undertaken in two steps: (1) The dc circuit analysis to determine the Q point. It involves the nonlinear equation or the load-line method. This is called bias analysis The fixed-plus self-bias circuit

  10. Self Bias Circuits Analysis of amplifier circuits is often undertaken in two steps: (1) The dc circuit analysis to determine the Q point. It involves the nonlinear equation or the load-line method. This is called bias analysis (2) Use a linear small-signal equivalent circuit to determine circuit parameters Analysis… Equivalent circuit find vGS vDS vGS

  11. Self Bias Circuits Plot of and Disregarded root for vGS<Vt0 Use only larger root for vGS and smaller for iD Example 12.2

  12. Self Bias Circuits Analysis of amplifier circuits is often undertaken in two steps: (1) The dc circuit analysis to determine the Q point. It involves the nonlinear equation or the load-line method. This is called bias analysis (2) Use a linear small-signal equivalent circuit to determine circuit parameters Analysis… Equivalent circuit find iD For saturation region vDS vGS

  13. Self Bias Circuits Analyze the self-bias circuit shown. The transistor has KP=50mA/V2, Vto=2V, L=10mm, and W=400mm Exercise 12.5 find vGS find iD find vDS

  14. FlexibleField Effect Transistors EE314

  15. Play video about plastic electronics http://www.plasticlogic.com Q: How we can do this? A: A new generation of MOSFETs for plastic electronics

  16. Transistor Feature Sizes http://www.hkn.org/imgs/bridge_sp06_figure2.gif

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