A. Parker EE 477L Fall 2010

Homework Assignment #4

due 10/4/2010 1st Floor of EEB, west side of building at 5 PM or

online using the DEN assignments function at 11:59 PM

Assume for the problems below that V_dd = 2.5 v, V_tp0 is -.7 v. and V_tn0 is .7 V. V_tpbodyeffect is -.9 v. and V_tnbodyeffect is .9 V.

Assume ß_n (k_n)= 219.4 W/L µ A(microamps)/V² and ß_p (k_p)= 51 W/L µ A/V²

You might want to wait to solve problems 7-9 until after the Thursday lecture.

1. a) (5 %) An NMOS transistor is used as a pass transistor. The input voltage is Vin = 1.0v. Vout = 0v at time t = 0. The final output voltage at t = infinity is Vout = 0.9v. What was the gate voltage Vg, assuming that Vg remained steady the entire time?

b) (5%) Does body effect occur when the transistor transfers 0's from input to output?

2. a) (7 %) Identify the sources and drains in a transmission gate at t=0+ when Vin = 0.7v. and Vout = 1.4 v. Vgn = 2.4 v, and Vgp = 0.2 v.

b) (8 %) What regions are the two transistors in when t approaches infinity? Be sure to justify your answers.

3. (10%) Compute the drain current flow IDS in a PMOS transistor when Vd = 1.6v, Vs = 2.0v, and Vg = 0.8v. Assume the transistor width is 14 lambda and the length is 2.5 lambda.

4. (10%) Compute the channel resistance of a unit size NMOS transistor when Vgs = 2.3 v and the transistor is in the linear region of operation. Vs= 0.1 v.

5. (10 %) A PMOS transistor has Vds = -1.8v. Vs = 0 V. Is the transistor is in the linear region of operation when Vgs = -2.2v.?

6. (10%) A PMOS transistor has Vgs = -2.0 V , Vds = -2.5 V. Vs = 2.5 v. What region of operation is it in?

7. (10 %) Assume that an inverter is on segment B of the input/output transfer curve. What is the minimum value of Vin that would allow the inverter to remain in the B segment after reaching steady state?

8. (10%) Now assume that an inverter is on segment D of the input/output transfer curve. If Vin = 1.7 v, what is the maximum value of Vout to remain in the D segment?

9. (10%) An inverter has the transistors sized so that as the input falls from Vdd to Gnd., a current spike occurs at Vin = 1.4v. What does that tell us about the ratio of betas of the two transistors?

10. (5%) What was the most surprising thing you saw on the fabrication videos?