NPN Transistor which turns on under 4mA

[linuxking]

Hi

I am tryin to locate a suitable NPN transistor which can be turned on by current under 4mA, I believe the 2N2222 needs like 15mA? The whole circuit is gonna be powerd by a 3V battery.

Thanks
Linux

 

[bogdanfirst]

there is not enough data to tell you what you need.
bipolar transistors are 'turned on' by current, that means that the more current you use to drive it, the more current it will let to pass.
if you want to turn on a transistor with 3mA, it can be possible, but it depends on the gain of it. i am not sure about the gain of the 2222 but i tiink it is around 100 or greater. anyway, the current it will let to pass is equalt to the product between the gain and the current you use to open it. if i say that the gain is 100 and the base emitter current is 3 mA then, the current that will pass trough the load is 300mA or less, depending on the load.

 

[linuxking]

3mA turn on and produce a 0.5A spike/pulse

Hi

Well wot I had heard was that 2N2222 needs atleast 15mA to "turn-on".

I have attached the circuit below

What I need a 0.5A negative pulse (very short one) I have arranged some caps and res so that when the transistor is on it generates a current spike/pulse, now the problem is I can only supply a maximum of 4mA to the transistor base, so which is the best npn to use for it, BC547? etc?

Thanks
Linux