Study Problems for Midterm 1

Prof. Parker EE 477 Spring 2006

Assume for the problems below that Vdd = 2.5 v, V_tp0 is -.6 v. and V_tn0 is .6 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

Assume Tox = 57 angstroms for thinox, and 5000 angstroms for thick oxide.

1. Compute the charge density in the depletion region of the channel of an NMOS transistor when N_A = 10¹⁶/cm³ . The value for q is given in the front cover of the text. Assume x_d = 50 angstroms.

2. Compute the worst-case gate capacitance of a unit size NMOS transistor using the dielectric constants in the front cover of the text.

3. An inverter with both NMOS and PMOS transistors in saturation has Vin = 1.6 v. Compute the ratio of the transistor ß's.

4. For the inverter in problem 3, what is the range of values of Vout at that point?

5. For the circuit shown in the homework 3 solution to problem 1 , which transistor(s) would be subject to the body effect?

6. A transmission gate is in the following state: V_in = 2.5 v. V_out = 1.9 v. At time t=0, Vg rises from 0 v. to 1.5 v. instantaneously. What region of operation is the NMOS transistor in at t=0⁺ ? As t approaches infinity?

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7. Two PMOS transistors are connected in series through shared diffusions. The gate voltage applied to both transistors is 0 v. The voltage at the input diffusion is 0 volts. Solve for the voltage at the output diffusion.