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EMITTER BIAS-LED DRIVER:-
Usually in the base bias led driver, the change in current gain (β) due to temperature changes, causes the Q point to change.
So, Emitter bias is used.
In emitter bias there will be no collector and base resistor, Because emitter resistor alone controls both the collector and base current
Calculation:-
Given:-
The emitter current, Ie≈The collector current ,Ic
The load current=Ic=10mA
So, Ie≈10mA
Vbb=5V
Solution:
Then,
Re, The emitter resistor=(Vbb-Vbe) /Ie
=(5V-0.8V) /10mA
Re=420Ω
Vcc must be greater than the Vbb
So, Vcc=Vbb+V(Load) =5+2=7V
Now, no matter how you change the beta value of the transistor, the Load current will be around 9mA to 10mA
And even if you increase the collector voltage up to the transistor voltage rating or Maximum voltage and power rating, the current will be maintained same
Don't decrease collector voltage, else the collector diode(based on npn construction) will become forward biased
This type of bias is used in Amplifier
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