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Midterm 2 performance
Full points is 48. Average is 37.75.
Small signal equivalent circuit example contd.
2
Common Collector Amplifier: Equiv. circuit
Notice that Rc = 0, and RE is not to be shorted. Thus emitter and collector switches position.
Also note that the current is directed upward instead of downward. So the sign of the voltage gain is positive,
unlike the common emitter case.
3
Voltage gain
4
Input impedance and Power gain
5
Output impedance
6
Output impedance contd.
7
Example
Calculate the voltage gain, input impedance, current gain, power gain, and output impedance of the emitter
follower circuit below
8
Output impedance
9
Chapter 5: Field Effect Transistor
5.1 NMOS Transistors
Major difference with BJT – there is no dc gate current.
Thus power dissipation is much less.
Figure 5.2 Circuit symbol for an
enhancement mode n-channel
MOSFET
The gate is insulated from the substrate or body using an oxide layer device characteristics depend on L, W, the doping
level, and the thickness of the oxide layer.
Gate used to be made of Al but now mostly it is made of highly doped polysilicon. Very recently, we have transitioned
back to metal gates to lower the gate resistance.