Homework Assignment #4

due 2/22/2011 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 8-9 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 = 2.5v at time t = 0. The final output voltage at t = infinity is Vout = 1.0v. What was the minimum possible gate voltage Vg, assuming that Vg remained steady the entire time?

b) (5%) What happens when the input Vin = 1.7 v?

2. a) (7 %) Identify the sources and drains in a transmission gate at t=0+ when Vin = 2.4v. and Vout = 1.4 v. Vgn = 2.4v, 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 an NMOS transistor when Vd = 2.5v, Vs = 0.6v, and Vg = 1.5v. Assume the transistor width is 12 lambda and the length is 3.5 lambda.

4. (10%) Compute the channel resistance of a unit size PMOS transistor when Vgs = -1.3 v and the transistor is in the linear region of operation. Vs= 2.4 v.

5. (10 %) An NMOS 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 = -1.0 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 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?

8. (10%) Now assume that an inverter is on segment D of the input/output transfer curve. Assume beta_n = beta_p. what is the range of voltages for Vout so that the inverter will remain in the D segment?

9. (10%) An inverter has the transistors sized so that the ratio of beta_p to beta_n = 4. What regions are the transistors in when Vin = 1.25v?

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