Electronic Devices - Transistor Bias Circuits - Discussion
Discussion Forum : Transistor Bias Circuits - General Questions (Q.No. 6)
6.
Which transistor bias circuit provides good Q-point stability with a single-polarity supply voltage?
Discussion:
1 comments Page 1 of 1.
SOORAJ JOSHI said:
1 decade ago
This is because, when the transistor operates,temperature at the junction increases;hence Ic increases.As a result of which,Ie increases.Due to this increase in Ie ,voltage drop across Re increases.This reduces the forward voltage across the emitter.Thus Ib reduces.
We know that,for any value of Ico, Ic=B*Ib+(1+B)Ico
where Ico=reverse saturation current, which increases as temperature increases & B=gain.
As discussed above,B and Ico increases and at the same time there is decrease in Ib.Hence above equation confirms that Ic can be maintained within limits.Thus the ckt is more thermally stable and the operating point is more stable.
We know that,for any value of Ico, Ic=B*Ib+(1+B)Ico
where Ico=reverse saturation current, which increases as temperature increases & B=gain.
As discussed above,B and Ico increases and at the same time there is decrease in Ib.Hence above equation confirms that Ic can be maintained within limits.Thus the ckt is more thermally stable and the operating point is more stable.
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