[UPSC CSE 2006] Digital Electronics/Microprocessors (Q338, 20M)

(i) Simplify the logical expression f = ABC + B \overline{C} D + \overline{A} BC by using Karnaugh map and realise f using NAND gates only. \hfill 10 (ii) The transistor in the following circuit has \beta = 100 and V_A = 90\text{ V}. What value of R_B will give 0 volt d.c. output \hfill 10