I HAVE GOT A PIC16F767 THAT HAS 3 HARDWARE PWM. I HAVE GOT THIS DRIVING 1 X 3 WATT RGB. WHAT I WOULD LIKE TO DO IS DRIVE 4 OR MORE 3WATT RGB LEDs.
I HAVE A FEW TIP41 TRANSISTORS LAYING AROUND COULD I US 3 OF THEM, 1 PER COLOR.EACH LED HAS ITS OWN CURRENT REGULATOR CIRCUIT.
THE TIP41 IS REATED AS FOLLOWS:
COLLECTOR BASE 40V
COLLECTOR EMITTER 40V
EMMITTER BASE 5V
COLLECTOR CURRENT 6A
BASE CURRENT 2A
A PIC CAN DELIVER 20mA AT THE PIN, BUT THE TIP41 REQUIRES 2A.
I HAVE LOOKED AT CIRCUITS FOR TRANSISTORS AS A SWITCH BUT CAN'T FIGURE OUT
WHAT RESISTOR TO USE ON THE BASE.
When using it as a switch, the actual required base current to get the rated Vce is ~Ic/10 as depicted on Fig 2 of the Fairchild data sheet.
Since all you have is 20mA, you will likely need a logic-level NFET (which draws no current from the PIC pin), or a Darlington NPN (which can be turned on with ~1 to 2mA). You can make your own Darlington by combining a 2n3904 with your TIP41.
That is a logic level MOSFET, check that you are buying the STP36NF06L and not a STP36NF06 - the L part has a maximum Vgs threshold at 2.5 volts, the non-L part maximum is 4 volts. The L part is characterized for an Rds(on) of 0.05 ohms at Vgs= 5 V, Id=15A.