1. EE314 Intel Pentium 4 Field Effect Transistors Equivalent Circuits

2. Chapter 12: Field Effect Transistors 1.Small-Signal Equivalent Circuits 1.Examples 2.Technology 3.Future Devices MOSFET Transistor

3. Current-Voltage Relations MOSFET Transistor NMOS transistor, 0.25  m, L d = 10  m, W/L = 1.5, V DD = 2.5V, V T = 0.4V Quadratic Relationship 00.511.522.5 0 1 2 3 4 5 6 x 10 -4 V DS (V) I D (A) VGS= 2.5 V VGS= 2.0 V VGS= 1.5 V VGS= 1.0 V TriodeSaturation V DS = V GS - V T cut-off

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

5. Load-Line Analysis of NMOS Amplifier Exercise: Draw the Load line R D = 1 k 

6. Load-Line Analysis of NMOS Amplifier Load line Taking i D =0 or v DS =0 we find out the load lane and the quiescent operating point Q for V GS =4V The quiescent values v in (t)=0 then i DQ =9 mA v GSQ =4V and v DSQ =11V Points A & B intersection of curve and the load-line for the maximum and the minimum gate voltage

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

8. 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 V G voltage as a function of V DD, R 1 and R 2 InputOutput +vG_+vG_

9. 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 InputOutput +vG_+vG_

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 Equivalent circuit Analysis… v GS v DS find v GS

11. Self Bias Circuits Plot ofand Disregarded root for v GS < V t0 Use only larger root for v GS and smaller for i D 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 Equivalent circuit Analysis… v GS v DS For saturation region find i D

13. Self Bias Circuits Analyze the self-bias circuit shown. The transistor has KP=50  A/V 2, V to =2V, L=10  m, and W=400  m find v GS find i D Exercise 12.5 find v DS

14. Flexible Field Effect Transistors EE314

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

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