# Electronics Transistors

1. Jun 5, 2010

### tomeatworld

Firstly, sorry if this is in the wrong section. I'll happily move it if it should be somewhere else.
1. The problem statement, all variables and given/known data
What is the impedence between the base of the BJT and ground of the common emitter amplifier circuit.

2. Relevant equations
Ic = IE

3. The attempt at a solution
So I started by saying that $$\Delta$$Vb = $$\Delta$$IE RE and that $$\Delta$$IE = $$\Delta$$IB hfe where hfe is the gain of the circuit. By then equating the two using $$\Delta$$IE I find that $$\Delta$$IB = $$\frac{\Delta V_{B}}{R_{E}h_{fe}}$$ so impedence is REhfe but this seems very simple considering the circuit. Am I missing anything?

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