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transistor is not getting off through pot

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yasir23

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my problem is that i want to on and off my transistor through pot 100k. but when i turn on power at 100k resistor so it is off. and when i start decrease its resistor when it become 33k ohm so transistor get on. but when i increase its reistor even 100k again. so it doesnt get off.
i m using 2n2222 transitor.

what could be the problem.

i m not getting understand
 

Hello,

Best is to post a circuit and to tell us how did you define "on" and "off".

Such hysteric behavior can be caused by parasitic oscillation.
 

Dear friends
Hi
The way for saturation is Give current to base of bjt. if your current is not enough , your transistor cant going to saturation region.
See it: region.JPG

region2.JPG
In first picture I gave current to base but it is not enough so bjt is in cutoff region. If you increase base bias voltage , so your bjt going to saturation region.
Or you can decrease the value of Base resistance( increase the base current)(second picture)
Ic = betta * iB
Best wishes
Goldsmith
 

yasir23 said:
my problem is that i want to on and off my transistor through pot 100k. but when i turn on power at 100k resistor so it is off. and when i start decrease its resistor when it become 33k ohm so transistor get on. but when i increase its reistor even 100k again. so it doesnt get off.
i m using 2n2222 transitor.
Click to expand...

It would be of interest to know what resistor you are speaking of (base, emitter, collector?)
 

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