- #1

curiousguy23

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## Homework Statement

Consider the following circuit

http://img109.imageshack.us/img109/80/circuit1.jpg

IL, current through R3 (unknown resistance must be found)

## Homework Equations

Vth=(Vcc/Rtotal)*R1 (V tThevenin)

Rth=R1//R2 (R Thevenin)

Vbe= 0.7 volts (silicon diode)

Beta (transistor constant)=100

Vcc=10v

IL=Beta*Ib

Ie=Ib + IL

## The Attempt at a Solution

I used the following Equation to try and obtain an answer.

Vcc= (Ib*Rth)+ (Ie*R4) + Vbe + Vth

Vth=5v

Rth=2.5k Ohms

Substituting gives:

10=(IL/Beta)*(2.5k) + 1000*(IL*((Beta +1)/Beta)) + 0.7 + 5

This yields an answer of IL=4.15mA.

My tutor said this is a wrong answer, the correct one is 4.3mA

What is wrong in my reasoning/Working?

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