Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

how to drive multiple transistors with same signal

Status
Not open for further replies.
A

ajaxoftherockies

Newbie level 4
Joined
Jul 16, 2016
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
45
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.

Thanks for suggestions!

- a -

LEDDrivers.jpg
 

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.
 

Audioguru said:
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.
Click to expand...

Thanks for the Mosfet suggestion. Do you have a part number for such a device? (not that i won't do my own search, just askin')

On my existing circuit, the LEDs are high-power ones on a Luxeon module; they draw around 800ma each and it is running just fine - no blown LEDs.

I'll look into the Mosfet idea and see what I can come up with.

Thanks for taking time to reply

- a -
 

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.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top