Transistors in parrallel to increase collector current

A 2N3055 power transistor has a max current of 15A. But at only 10A, it turns on poorly even with a whopping 3.3A of base current.
Without saturating, at 10A its minimum current gain is only 5. Its current gain isn't spec'd at higher currents.

i am using a dalignton pair, a TIP122 and/or TIP 140.. this should solve this problem, right? because the current gain is very high.. am i right?

You didn't say how much output current.
A TIP140 has a max continuous output current of 10A. With an input of 40mA, its max saturation voltage is 3V. That is 30W of heat wasted and the motor's voltage will be reduced.

Anyway, why don't you use MOSFETs?

mosfets are much more expensive... as i found in my country..

Does anyone knows a mosfet that can handle 10A coninuous, low voltage, not too expensive?

All Mosfets here are at least 33A and are pretty inexpensive.
Low gate voltage ones are available but I don't know any.
Why aren't ordinary electronic parts also inexpensive in Egypt?

Surely it's cheaper to buy four MOSFETs rather than eight or sixteen BJTs.

do you have documents about H BRIGGE ?
can you share for me ?
thanks a lots

ikalogic said:

how can i use emitter ballast resistors in an H bridge ?

Click to expand...

well yer... only if you really have to, get some FET's instead their neg-temp coef means they share current alot better then BJT's in //el.
But if you have to you have to

ikalogic said:

can i use it for darlington pair transistor?

thx a lot.

Click to expand...

yup, a darlington is just a high-current trasistor with a low-current trasistor as a base-drive to get the benefits of higher current and higher BETA

but they are slow and depending on what you are doing with yr H-bridge (ie are you going to be using PWM to control the voltage?) then the question has to be ask are BJT's really worth the hassle?


--OT--
OMG hte smilies have become useful hm:hm:hm:


--EDIT--
Arr beaten by the ninja-edit, he did write what I quoted, honest