Problems BJT dc analysis PDF

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EEE311- Problems /BJT-JFET DC Analysis Vo

Q1) Vδ = 0.7 V, Vbe=0.7 V, β=100 6V

(a) Find the required V2 voltage in order to enter the transistor saturation when V1=0 V. 10 K

(b) Find Ib, Ic, diode currents (Id1, Id2), Vbe and Vo for V1= V2=8 V and V1= V2= -5 V. V 1=V2, V

I b, mA

I c,mA

Id1 , mA

Id2 , mA

Vbe, V

1 KΩ

V o, V

D1

D2

8

V2

V1

-5

Ans: No solution for V1= V2=8 V Vs= 5

Q2) Find Id, Is , Ig, Vgs, Vo , Vx, Vds, state and region of JFET for Vi= 0,-3 and 3 V. Idss=4 mA, Vp=2 V Vi, V 0

Id , mA

Is,mA

Ig, mA

Vgs , V

Vo , V

Vx, V

Vds, V

state

Vx

region

1mA Vo

-3

Vi

3 Vdd= 12 V

Ans: Vds= ─ 4V, ─ 1V, ─ 7 V for Vi = 0, ─3 and 3 V

Vd= ─5 V

T1

Q3) Find the Id and Vds voltages of both transistors. Vp= -2 V, Idss=6 mA. Rs1=1 K

Ans: Vds1= 10.816 V, Vds2= 11 V, T2 200K

1mA Vss= -12 V

-12 V

12 V

Q4) Use one alpha analysis to find operating point of each transistor and

Ans: Vce1= ─ 5.7 V; Vce2= ─1.2 V

I2 0.5 mA

V I2

Voltage drop across the constant currents sources. Vbe= ─ 0.7 V I1 2 mA

VI1

3K

I3 0.25 mA VI3

3K T1

5K T2 3K

4K 2K ─9 V

5V

Q5) Vδ = 0.7 V, Vbe=0.7 V, Vce,sat=0.2 V β=20. (a) Assume the transistor in figure is cut off and the diode ON.

5K 5K

Test the assumptions. Clearly state any contractions you find or verify the assumption. D

5K

(b) Assume the transistor in figure is active and the diode ON. Test the assumptions. Clearly state any contractions you find or verify the assumption. (c) Assume the transistor in figure is saturated and the diode ON. Test the assumptions. Clearly state any contractions you find or verify the assumption

Vcc=15 V

Q6) The Zener diode in given figure has Vz=7 V and Vγ=0.7 V. If IL=20 mA and β=50 7.8 K (a) Find collector current and Zener current

T2

Vo

(b) Find output voltage and collector-emitter voltage 4. 7 K

(c) Determine the state of Zener diode and state and region of transistor

IL

Ans: Vce=8.7 V Vx = 9 V

Q7) The simple two-resistor bias circuit shown in figure can be used to bias transistor. β=50, Svbe= 0.7246 mS. Find R, Q-point Q(Ic, Vce), Vbe and base voltage. Ans: R= 1K Vcc=10 V

Q8) For given BJT circuit β=100, Vγ1=0.7 V, Vγ2=2 V (for LED) Vi is bipolar square waveform having a peak to peak voltage of 8 V

RC=1 K

and frequency of 100Hz. (a) Draw Vi , Vbe, Vo , ID1, Ib, Ic, Iled on the same scale.

18 K

R

Vo Vi

RB=10 K

D2

(b) Find the critical input voltage level that makes LED is ON.

Ans: (b) Vi...