How to make transistor ON

[electronicsLearner77]

I want to know how to make the transistor "ON". If the Base voltage is greater than Emitter voltage by 0.7V is one standard way i know and with collector connected to VCC. One configuration i want to know is if the collector is connected to -VCC and the Base voltage is less than the Emitter voltage, Can it be made "ON"?

 

[Alec_t]

Sort of. For an NPN transistor, if the base is taken negative far enough (typically about 5-6V) with respect to the emitter then the base-emitter junction breaks down and current can flow. But the breakdown damages the transistor to some degree.

 

[Nanren888]

Look up circuit configurations for NPN & PNP transistors.
The symmetry of these may be what you are looking for.

For example from
https://www.electronics-tutorials.ws/transistor/tran_2.html


and
https://www.electronics-tutorials.ws/transistor/tran_3.html


Ok, more troubles with even small images
The third image down from these pages.
https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/transistor-tran44.gif
Moderators note : uploaded picture in stead of direct linking

 

[electronicsLearner77]

Sorry for missing critical information i am referring to an NPN transistor.

 

[Harald Kapp]

Read this resource, please.

 

[Wollowstone]

Sure. Assuming the Vbe > Vbe_on, you will be in deep saturation, with almost or no "amplification" at all (the "beta" value won't be what you expect, though, probably close to 1, since beta is relatively more or less constant at low frequency, but only in active mode, not as you pass into saturation mode, that is, when Vb becomes equal or greater tha Vc). With Vbe > Vbe_on and Vb >> Vc, both diodes are simply forwarded biased. Not of a great interest though.

 

[ratstar]

Maybe u have the collector and the emitter the wrong way around.

 

[Wollowstone]

Additionnal note: You can use simulator for those circuits, if you don't want to blow off your components. Under TINA and CircuitLab, you can use the NPN as defined by default; under LTspice, you have to specify the parameter Br ( beta reverse) since by default, it is set to 1.00 and not often written over this default value by the specific model for a given NPN.