Question

Question 4 (25 Marks) (5) 1. Derive the Dynamic Emitter Resistance, re that is used in the re-model small-signal analysis of BJT. 2. The circuit in Figure 7 shows the multistage cascade of two single transistors with B=100. Given the value of Vpp=12 V, R1=120 kN, R2=40 kN, R3=100 ks, Ra=30 kn, RE1=3.9 kN, Rez=4.5 kN, Rc1=6.5 kN, Rc2=8 ks, (2) (4) (a) Identify the transistor configuration for all stages. (b) Determine the d.c collector current (Ici and I cz) and voltage (Vciand Vc2) of each transistor. (c) Draw the re-model small-signal equivalent circuit of the entire amplifier and determine the values of all its components. You may neglect ro1 and ro2. (d) Determine the input resistance, Rini and Rin2 for Rs=5 kN. (e) Determine the overall gain, ve/v, for Ry=2 kN. (6) (4) VOD VDD Rc1 R3 GR 62 SR1 8 00 w VO + RS Vb1 4H Q1 Vb2 Q2 R2 Vs R4 RE1 = Ž 00 WW RE2 8 HI HI IH HI Rini Rin2 + 5 I 5 Line Figure 7

Answer 1

Voo NDD Ira 3 Vo ERE amplifier of Rin! amplifer -2. Rinz VOD 312V ß 3100 R1 = 120k & R2 240kr Ry=30k62 23.9812 Rez 24.5k2 RB 100 kr REI TE Re & 6.5 Re, z8kr. VE " Dynamic reesistan me a Vg 225 mv. 30 Do ve analysis for both the BJT. so capacitors will be open cirloited as frequency: of the De =0. (1) for amplifer 1 De malyus. 120x40 RB, Rth a 160 30kr. Nth a UDD R2 RI RITRE YOK 160 3V. RIIR2' VDD = 12 Rei 12 X R2 Rei VBE 2017 NOD Be=BIB 11+BIR TE put kul to input loop 6-ska RBI & Boka 3V 213 BOKS2 - VBE - (HB)13139962 1-19 VIE ERE 23.9K2 7(80 – 0.7) = 1a (301loºt(10113-93189) 7 2-3 = 16 (423.944 2.3 428.9ka, 5.42 x 106 IB 2 2 5.42 MA. TES (4B) TB (100+1) 75.4262A. 5.48 8104 A 0.548 MA res cre fore startage stage 1) V1 25x103 2 Meia ..osuma It 462:962, for stage - 2 Roz z Rth 2 Yth = VOD 100kr X Boka R3 ) Ry 130KS. 3 23:07K2 Ry Rejt Ry 30 712 = 2.77 V. 130 VDD - UBE 12-07 RB + B)Re, 28.07K24 101x4.567. 11.2 28.66 WA. 477.57 KA.

RE=3.9kr 2770. TE (B+1) 16 101 X 28.66 MA 2.39 MA. rea VT IE 25 mv 2:39MA 10.461 2. B)(0) Traveister contigeeration for stage - common emitten Volfage eleviden circuit common emittere Noltage devider circuit statge- 2 → Foll" All stage stage ~ Multi common emitter Re food coupled cincuit. multistate 15 ) Ich calcutate By De analysis and Tee & vez ver Previous De analalysis NDO =12r. circuit. VOD -128 Rex 26.5kn. 8k ?? vez. 23.07k2 3 OK • Va RBi. 4.SKA, 3. stage a stage-21 for stage 2 18 25.42 MA IG = BIBI 100 85.4QUA 0.542 MA. - VDD - fare Na 2.12- (0.549X 6.5) 28:479V. I B2 2 23.66 MA Il 2 B DB2 = 2.366 mA. sloo X.23.66 des Nez z VOD Ical Re (2.366 MA X8 KB 12 2 - 6.928 V,

(@) for small og nal analyer's all capacito a cerill small segnal equivelent short cirecuit then Cercent. Biba BRUS RB SRL RBL Biby Ring Rina Ring Ring Rini 2 Ring 22 Bree 2 100 X 462.96 46.296Rs. RB, Il Bree BOKSL X 46.296 (30+46.296)KA 2. 18.203 ką Ring Breez 100 X 10.461 2 1.046 KR. Ring. 2 11 23.07kR:X 1.046 8106 [ 23.07 +1.0467k2 2 1 KQ e) voltage gain fore stage 2 Re 22k ? AV2 RL 2x103 They - 191.186 10.461 voltage gain fore stage 1. ANI Rei 2 2 6.5ka 462.96 al4.04 ren overcal gain 2 Avo X AVE 191.186 X 14.09 2684.268 Scanned with CamScanner CS Scanned with CamScanner