A. Parker and A. Zadeh EE 477L Fall 2008
Homework Assignment #4
due 10/06/08 at 9 am either in the boxes in EEB or
on line using the DEN assignments function
Assume for the problems below that Vdd = 2.5 v, Vtp0 is -.6 v. and Vtn0 is .6 V. Vtpbodyeffect is -.8 v. and Vtnbodyeffect is .8 V.
Assume ßn (kn)= 219.4 W/L µ A(microamps)/V2 and ßp (kp)= 51 W/L µ A/V2
1. a) (15 %) An NMOS transistor is used as a pass transistor. In an effort to improve some aspects of the circuit, the threshold voltage is raised to .9v. Does the pass transistor transfer 1's better or worse than before. Try to be quantitative in your explanation.
b) (5%) Does body effect occur when the transistor transfers 0's?
3. a) (10 %) Identify the sources and drains in a transmission gate at t=0+ when Vin = 0.75 v. and Vout = 1.75 v. Vgn = 2.0v, and Vgp = 0.5v.
b) (10 %) What regions are the two transistors in when t approaches infinity? Be sure to justify your answers.
4. (7%) What is the effect of using a gate insulating material that has a lower dielectric constant than conventional CMOS?
5. (15%) Compute the maximum possible drain current flow IDSin an NMOS transistor when VDS = 2.5 v, and VGS = 1.7 V. Assume the transistor width is 12 lambda and the length is 3 lambda.
6. (12%) Compute the channel resistance of an NMOS transistor when Vgs = 1.0 v and Vds = 0.1 v. Vs=0.2 V.
7. (12 %) An NMOS transistor has VDS = 1.5 V. VS = 0.0 V. Is the transistor is in the linear region of operation when VGS = 1.1v.?
8. (14%) A PMOS transistor has VGS = -2.0 V , VDS = -1.1 V. VS = 2.5 v. What region of operation is it in? Now assume VGS = -0.2 V, VS = 1.5 v, and VDS = -0.2 V. What region of operation is the transistor in?