I have a working circuit that has three separate signals processed from an audio input.
The output signals drive a tri-color LED at about 700ma per color. Each color/LED is driven by a TIP120 transistor.
(schematic below shows three signal inputs on R23 R25 and R28 that drive the TIP120s)
Right now, the TIP120s work fine but a bit warm - nothing the heat sink can't handle, though.
Next I would like to scale this up, but am not exactly clear on how I get the output signals to drive additional transistors.
Or is the answer a more powerful replacement of the TIP120s? My final current requirement will be around 25 amps.
A TIP120 is not a single transistor, it nis two transistors connected as a darlington.
Your circuit has nothing to limit the LED current so the LEDs will blow up.
The maximum allowed current in a TIP120 is only 5A so you should use a powerful Mosfet for 25A.
A TIP120 is not a single transistor, it nis two transistors connected as a darlington.
Your circuit has nothing to limit the LED current so the LEDs will blow up.
The maximum allowed current in a TIP120 is only 5A so you should use a powerful Mosfet for 25A.
You MUST limit the current to the LEDs with a resistor or a circuit. You must be lucky that your LEDs are not damaged (maybe they are damaged but have not failed yet).
An IRFZ44 Mosfet can pass 36A to 50A depending on how well you cool it. Its gate-source needs 10V for it to completely turn on.