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Topic: TIP102 vs TIP120? (Read 3903 times) previous topic - next topic


Are these transistors interchangeable?  I am trying to drive a relay from a digital out on the Arduino.

Thanks in advance!


The short answer is yes.  And I found the data sheets on my own.... they just don't mean anything to me.  It might as well be written in hieroglyphics.


The TIP102 has a Vceo "collector to emitter breakdown voltage" of 100 VDC as aposed to 60 Volts for the TIP120.  thats pretty much the only major difference.  switching anything under 40 Volts, i would just use what ever you find easiest to get your hands on.



Also, do you really need a Darlington transistor? any relay that requires less than 200 mA can be driven with an ordinary GP "general purpose" NPN like a 2N2222 or a 2N4401.  look for the Hfe specification on the transistor data sheet.  Hfe is the DC current gain.  A transistor with a minimum Hfe of 80 will draw less than 2.5 mA from the pin of the micro controller while driving a relay coil that needs 200 mA to close.  The TIP102 has a  minimum Hfe of over 1000 and would close a relay that required over 2 amps without drawing 2 mA from the micro controller pin.


El cheapo relays that I had laying around were 9V.  5V signal from arduino to Tip120 to switch the 9V for the relay. I'd have bought 5v relays if r$ had them in stock.

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