# how connect transistor tip142 to pic

Discussion in 'Homework Help' started by hertz.12, Jan 24, 2016.

1. ### hertz.12 Thread Starter Member

Apr 25, 2015
36
0
hi
i m trying to interface tip142 and tip 122 to pic 16f628 to drive 10A load....the problem is i don't get 10A out..only about 7A out and the tip 142 get hot after 5minutes ..not too hot so it is ok but i need 10A..what is wrong?

2. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
You are saying that your load is 1 Ω and that it is powered from 9 V. How do you expect to get 10 A into it in the first place?

Look at the data sheet for the TIP-142 and you will see that the Vce saturation voltage at 10 A (and Ib = 40 mA) is spec'ed to be less that 3 V. So even if you only got 6 A you would have nothing to complain about.

3. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
Did you know that both the TIP122 and the TIP142 are Darlington transistors? You do know what that means -- Right?

4. ### hertz.12 Thread Starter Member

Apr 25, 2015
36
0
yes i want 9A not 10A.....

why i can't get 9A from tip141? now i get 6A no more...what is the wrong?

5. ### hertz.12 Thread Starter Member

Apr 25, 2015
36
0
yes i think i know both Darlington transistor

6. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
You start with 9 V. You have a transistor that saturates with as much as 3 V from collector to emitter. That leaves 6 V across your load, which is 1 Ω. How much current will flow through a 1 Ω load that has 6 V across it?

7. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
So why are you using two Darlingtons in a Darlington configuration? The TIP-142 has a beta of ~500, meaning that to support 10 A you would only need 20 mA of base current. What can the PIC provide?

8. ### hertz.12 Thread Starter Member

Apr 25, 2015
36
0
yes i think pic can provide 20-25ma but i prefer not to reach maximum pic output...i will use npn2222 instead of tip122

i thought that tip 141 can drive 10A load...there any way i can drive 9A with tip141?
thanks

9. ### WBahn Moderator

Mar 31, 2012
18,085
4,917
It can. Make your load 0.5 Ω and you will see. It's not the transistor that is limiting your current.

10. ### Bordodynov Active Member

May 20, 2015
670
194
See

absf likes this.
11. ### Bordodynov Active Member

May 20, 2015
670
194
From my pictures easily calculate the power transistor.
7.606A*1.394V=10.6W !!! We need a big heatsink!

8.933A*66.86mV=0.597W You do not need a heat sink.

12. ### hertz.12 Thread Starter Member

Apr 25, 2015
36
0
thank you all....good info