I need to control a 6 volt 100w watt incandescent bulb with my Arduino. I was thinking of using a TIP35C transistor but I realized the 40mA(max) output of the pins on the Arduino would be inadequate.

Is it possible to use one transistor to drive another to achieve this effect? For example the Arduino switches a TIP120 which switches the TIP35C. If so how would this look?

Is this an overly complex way to do it?

  • 1
    \$\begingroup\$ Why not use a darlington transistor in the first place? \$\endgroup\$ Sep 14, 2015 at 18:33
  • 2
    \$\begingroup\$ Probably better off using a logic-level MOSFET. \$\endgroup\$
    – John D
    Sep 14, 2015 at 18:35
  • \$\begingroup\$ What John D said, switching that kind of current is no place for a BJT in 2015. \$\endgroup\$
    – Matt Young
    Sep 14, 2015 at 18:36

1 Answer 1


6V at 100W is about 17A and you can expect a turn-on surge of perhaps 10x that.

A Darlington, even if you could drive it, would eat 15-20% of your voltage (datasheet says it could drop as much as 4V at 25A and meet specs!).

I suggest you use a fat MOSFET. For example, a PSMN1R1-30PL

  • \$\begingroup\$ Thank you so much! That looks like exactly what I need. Do you think something like this would do it? sparkfun.com/products/10213 \$\endgroup\$
    – annie
    Sep 14, 2015 at 18:41
  • \$\begingroup\$ It will get quite hot and will require a large heat sink. Also drain current pulsed rating is marginal. I suggest a better part above that will run cool, and is still not very expensive ($3 in singles). \$\endgroup\$ Sep 14, 2015 at 18:52

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