Question

(a) Explain physically how ap-n junction functions as a rectifier diode. (5 marks) Figure Q5(b) shows a Voltage divider bias circuit for a BJT. Given that; Vcc 18 V, BDC (b) 120. 18 V 3.3 kQ C2 39.0 kO 10 μF C1 B 120 10 μΕ 1.0 kQ 8.2 kQ Figure Q5(b) Voltage divider bias configuration of BJT Calculate Ic and VCE using exact method. (i) (5 marks) Repeat the calculation of Ic and VCE using approximate method. (ii) (3 marks

Answer 1

L8V Guien the current o Voltage Dunder Bes. DC Cireriet Analyses - Consider Dc Souree only. ve: 18V I, Ic Rc 3.3 Oz Rth tp vee. Minik=120 - Vih. O t id Rei T T 1. oker T RI I 39 KL Re § 3.3 kr 8.233 RE . 3 1. Oker (Themenin equivalent cuint) Vth - Vec. Rz Ritrz 18.8.26. (8.2K+3916) 3.127V Roth - Rill Rz 396x8.2K 16.475 KR. 39K+8.2K Then, Applying RVL un Theremin's equivalent currit, Vth - Ib Rth - TE RE :0. → But It - Tc- BTB for Cermin Emiter Amplifii Then, Egn © » With - IB Rth - BIB Re 20. Vthe IB C Rth + PRE) IB . VAR Rith + BRE.

3.127 = 2.466 X10A (6.745x60°)+(120x 1 xL03) Then. Ic - Te - BIB = 20x2: 466 x 100 A = 2.96 XLD A. Applying KvL form Vee to ground, nue gut Nee - Tc Rc - VCE - TE RE :0. Then Vce : Vec - Ic Rc - IE RE Sri Ic Ie, Ves - Vee - Ic (Retre) = 18- (2.96%w%) (3.8k+1K) 218 - 12.198 = 5.2 V Ic = 2.96x1'A VE : 5.27 V. Guen the commit ® Tret self beaning DC Cunit Analysus - Censueler bc Sounes esity. p Vpp *lov RD: 50002 ws Vos Ip: GMA * Rs : soor Is - Ip

Applying KvL from Upp to ground, the gut Vop - Ib Rp – Vos - Io Rs = 0. VDs Vpp - Ip C Ro+Rs) = 10- (S.xtbº) (500+500) . 10-6 24V For. JFGT to be buired in Saturation regain, VGs is should be re and should satisfy the Condition, [Ups z Vas - vp / whee Up is punch-coff valtuge of JFET, described in deta sheepe.