1. EE210 Digital Electronics Class Lecture 8 June 2, 2008

2. 2 MOS Field-Effect Transistors (MOSFETs)

3. Mid-Term Exam Solution

4. 4.4 MOSFET as an Amp and Switch MOSFET in Saturation Acts as a Voltage- Controlled Current Source Changes in Gate-to-Source Voltage v GS gives rise to i D Where v DS = v GS -V t

6. 4.41 The Transfer Characteristic Basic Circuit most commonly used for MOSFET Amplifier – Common Source or CS CKT Because grounded Source Terminal is Common for both Input and Output v GS = v I and controls i D Output v O is obtained in R D v O = v DS = V DD – i D R D Assume v I to be 0 to V DD we analyze ckt to determine output v O that is VTC of CS Amplifier

7. 4.4.2 Graphical Derivation of TC

9. 4.4.3 Operation as a Switch To use as Switch, the MOSFET is operated at the Extreme Points of the Transfer Curve Device is OFF for v I < V t and Operation is at Segment XA with v O = V DD Device is ON when v I is close V DD and operation is close to point C with v O very small, v O = V OC at point C Transfer Curve is similar to the form in Chap 1 for Digital Logic inverter MOSFET CKT can be used as Logic Inverter with ‘Low’ voltage Level close to 0V and ‘Hi’ level close to V DD

10. 4.10 The CMOS Digital Logic Inverter The Basic CMOS Inverter Utilizes two MATCHED enhancement type MOSFETS: Q N (n- channel) and Q P (p- channel) Body of each is connected to Source

12. 4.10.1 Circuit Operation Consider Two Extreme Cases v I = 0 (logic 0 level) and v I = V DD (logic 1 level). In both cases consider Q N is driving and Q P is Load (due to symmetry opposite will be identical)

15. 4.10.2 Voltage Transfer Characteristic (VTC)