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Biasing Circuit
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Establish a constant voltage VB.
Current-derived negative feedback.The degree of
success of the negative feedback is Bias Stability.
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cut-off conditions,
Example
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A transistor is to be biased at a collector current of 1 mA when a 12-V power
supply is applied. Using the above figure, determine the values of R1, R2,
and RE if 3.4 V is to be dropped across RE and if the current through R2 is
to be 10 IBQ. Assume that for the transistor used, VBEQ = 0.6 V and hFE =
100.
Example
Also, VB = VRE + VBE = 3.4 + 0.6 = 4 V.
VR1 = VCC – VB = 12 – 4 = 8 V
Common Emitter Amplifier
Common Emitter Amplifier
Common Emitter Amplifier
Transconductance=how much IC changes with a
fluctuation in VBE.
In practice, VT = 26 mV at
room temperature
The terminal voltage gain is therefore
Model
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Basic Equation
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Equivalent Circuit
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Simulation model