RGB LED driver, Any comments?

[cjurczak]

Seems everyone is using MOSFETs to switch their RGB leds, any reason not to use a darlington pair?

[skimask]

Seems everyone is using MOSFETs to switch their RGB leds, any reason not to use a darlington pair?

MOSFETs don't have a secondary breakdown when they overheat, so less chance of burning up. Mainly, no base resistor needed, lower drain-source resistance, practically zero gate current required (gate cap's make it draw a bit of current at high freq's, not much though.

The list goes on...

[T.Jackson]

MOSFETS are a voltage controlled current source as apposed to BJT's which are a current controlled voltage source. FETs in general have a relatively higher impedance than their BJT counterparts.

I think there's a lot of personal preference between the two. I will make a bold statement and say that "BJTs make better audio amplifiers" In many cases, either of the two can be made to work.

[Docedison]

No, however they will require more heat sinking than a Mosfet of equivalent current capacity. Since it is a switch (PWM) the LOW RDSon of most all power mosfets < .1 Ohm Vs a VCEsat of > 1Volt makes it a kinda No Brainer unless all you have are some tip121's? I don't remember which... But @5V gate voltage an IRF 540 is hard to beat for a GP Power Mosfet.
Doc