# Homework Help: Another transistor problem

1. Jun 30, 2010

### kliker

[PLAIN]http://img256.imageshack.us/img256/2164/transistor.jpg [Broken]

i should find Re so that transistor works in saturation region

also i should find Ib in saturation region

Rc=2kΩ , R1=2kΩ , EB=5V, Vcc=10V, V1=3V, β=100

im really confused with R1 and V1 i dont know what is their function

i know that in saturation region Vce = 0

also from the diagram i can see that

Eb - 0.7 = Vre so Vre = 4.3 Volts

Ie = Vre/Re

if we assume that Ie = Ic

then

Ic = Vre/Re

Ic is Vcc/Rc = 10/2000 = 5mA

so Re should be Vre/5mA = 4.3/5*10^-3 = 0.86 KΩ

but does this Re stand for saturation region?

Last edited by a moderator: May 4, 2017
2. Jul 1, 2010

### chaoseverlasting

Your calculation for Ie doesnt take into account current flowing due to Vcc or V1 in the resistor Re. Use Kirchoff's laws.

3. Jul 1, 2010

### kliker

we have

Eb - 0.7 = Ic1*Re we find Ic1 from Eb

Vcc - Ic(Rc+Re) - Vce = 0
V1 - Ic(R1+Re) - Vce = 0

we find Vce from these two statements and Ic which I will have to add Ic1?

and how can this help me solve the problem?