Homework Assignment #4
EE 477 Fall 2012 Professor Parker
Hardcopies due in the course boxes on the third floor of EEB 5 PM 10/08/12
Ecopies due 11:59 PM 10/08/12 using the "Assignment" Function on DEN
To ensure academic privacy, please use a cover page on your homework hard copies that does not contain any work.
Assume for the problems below that Vdd = 2.5 v, Vtp0 is -.7 v. and Vtn0 is .7 V. Vtpbodyeffect is -.9 v. and Vtnbodyeffect is .9 V.
Assume ßn (kn)= 219.4 W/L µ A(microamps)/V2 and ßp (kp)= 51 W/L µ A/V2
1. (10 %) Identify the sources and drains in a transmission gate at t=0+ when Vin = 2 v. and Vout = 0.0 v. Let Vgn = 2.0 v, and Vgp = 0.0 v.
b) (15 %) What regions are the two transistors in when t=0+? when t= infinity? Be sure to justify your answers.
2. (10 %) Assume that an inverter is on segment A of the input/output transfer curve. What is the minimum value of Vout that would allow the inverter to remain in the A segment after reaching steady state?
3. (10%) Now assume that an inverter is on segment D of the input/output transfer curve. Assume betan = betap. what is the range of voltages for Vout so that the inverter will remain in the D segment?
4. (10%) Compute the channel resistance of a unit size PMOS transistor when Vgs = -1.1 v and the transistor is in the linear region of operation. Vs= 2.4 v.
5. (10%) Assume an inverter is on segment D of the input/output transfer curve. If Vin = 1.6, what is the maximum value of Vout that would allow the inverter to remain in the D segment?
6. (10 %) Why is there a current spike on segment C of the input/output transfer curve? If the C segment occurs when Vin is greater than Vdd/2, what does that tell us about the ratio of the transistor betas?
7. (10%) An inverter has the transistors sized so that the ratio of betap to betan = 2. What regions are the transistors in when Vin = 1.2v?
8. (7%) Why do we require any p+ diffusions in the nwell to be spaced away from the edges of the well?
9. (8 %) When a positive gate voltage is applied to an NMOS transistor, and a depletion region is formed, is there a net charge in the depletion region? If so, is it positive or negative?