Ways to reduce sensitivity of darlington pair

Is there a way to reduce the input "sensitivity" turn-on voltage of a darlington pair? to be use with a 50k pot to drive a small DC motor load?

Can I put a resistor in series between a different point between the transistors to reduce gain?
I have 1kohm 10kohm and 100kohm resistors to use

I would like to keep the linear input with no voltage/current at the 50kohm pot on the input all the way off
and full voltage/current at all the way on.

I had an idea to take the negative voltage and put a tiny current to the "base" to reduce gain but thats not efficient in power consumption and limits output power.

Could I possibly skip the darlington type and use a single NPN transistor with a resistor to bias it to just below turn-on voltage?
I could then use a resistor in series with the pot to take away excess current from the pot to get 0v to full v of output from the transistor?
 
Hi Guys

You need to look at how a BJT works.

Essentially (and as a first approximation) the transistor conducts no current until the diode junction of the base-emitter turns on at around 650mV. At that point it only takes milliVolts of change to cause amperes of conduction change through the emitter to collector path. So, it is easy to see that simply using a pot to control the base directly is not so straight forward.

If this is the same app as in the other thread about controlling a motor, then you need a bridge as described there (due to the low battery voltage being used).

Have fun
 
It is a triple diffused NPN used in high power 40W+ applications that i have two NPN's of

With a 12v power supply to use which supplies 1.5A current max
Motor only uses 0.55A at 12v

Weird thing about this specific one i have. Its possible to reverse collector/emitter and still function correctly though i don't use it like that normally.
 
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