Transistor replacement from low current to high current capability.

Hie everyone quick question:
since i cant find a decent motor driver cheaply, i was wondering if buying one of these and just replacing their transistors with higher current rated ones.
This one is a 15A. what if the npn and pnp transistors are replaced with mosfets that can handle 27A?

what do you think?

MOSFETs are not direct replacements for bipolar transistors. By the time you finish "hacking" the board, I'd guess you are better-off building one from scratch.

If you can find higher rated bipolar transistors, it might work. But, you'll probably need to add heatsinks. I'm skeptical that board going to handle 15 Amps as-is without heatsinks (but that's just my gut instinct, and I've never built a motor driver).

The controller you linked too is a MOSFET dual H-bridge using IRF3205's rated
at 110A. That's not the issue, the issue is heatsinking - adding heatsinking and
fan will increase the current carrying capacity.

But eventually higher currents will cook the connecting traces on the PCB, so 15A
continuous may well be the sensible limit.

The controller you linked too is a MOSFET dual H-bridge using IRF3205's rated
at 110A. That's not the issue, the issue is heatsinking - adding heatsinking and
fan will increase the current carrying capacity.

But eventually higher currents will cook the connecting traces on the PCB, so 15A
continuous may well be the sensible limit.

so just to confirm, as long as i have good cooling and and better connecting traces i can carry it up to 30ish amps?

Low VCE(sat) Bipolar Transistors are miniature surface mount devices featuring ultra low saturation voltage VCE(sat) and high current gain capability. These are designed for use in low voltage, high speed switching applications where affordable efficient energy control is important.

Looks like a copy & paste definition from somewhere ...

tawandapro:

The controller you linked too is a MOSFET dual H-bridge using IRF3205's rated
at 110A. That's not the issue, the issue is heatsinking - adding heatsinking and
fan will increase the current carrying capacity.

But eventually higher currents will cook the connecting traces on the PCB, so 15A
continuous may well be the sensible limit.

so just to confirm, as long as i have good cooling and and better connecting traces i can carry it up to 30ish amps?

IRF3205's have 8 milliohm on resistance - the rest is simple physics, heat dissipation is
I-squared-R, and heatsinks will have a degrees-C per watt rating.

30A means 7W per device, 50A means 20W per device.

The picture is a little more complex with PWM as there will be switching losses, and
those are dependent on the gate-drive circuitry as well as PWM frequency and supply
voltage.

Add some chunking Al heatsink to those MOSFETs (with insulated mounting hardware)
and it should go quite a long way. However you have to be a little wary, more current
means more gate charge is needed so the switching may slow down a little.