View Full Version : Darlington TIP120 transistor switches

03-01-2005, 06:06 AM
I am not clear on the data of switching transistors..

Are the Bases of Darlingtons pulled to ground internally?

Should I pull Stamp pins to ground when using NPN common and high-gain transistors?

How should I calculate the TIP120 Base to Stamp pin resistor? (hfe 1000 at 3 V.) (solenoid valve 12 V. 500 ma. plus spike?) Would 220 ohms cover the bases?

The data says Base max current is 120 ma. How could that happen?

I read that IN4004 snubbing diode is added to the TIP120. Is this necessary?
(I also read that the heat sink tab is grounded to the Collector.)

03-01-2005, 06:10 AM
Treat the TIP120 just like the 2803, except put a 1K resistor in series with the base of the transistor. That all there is to it.

Sid Weaver
Do you have a Stamp Tester?

http://hometown.aol.com/newzed/index.html (http://hometown.aol.com/newzed/index.html)

03-01-2005, 06:20 AM
That is so easy, thanks!