Hi. I am having an issue with a TIP142-based H-bridge circuit which I need to switch 48V@5A through.
The TIP142s have their base connected to the Arduino via 2k2 resistors and the collectors and emmitters connected directly to the 48V, Load, and GND as one would expect. The switching itself works fine with the voltage swinging between positive, zero and negative as the arduino drives the H-bridge between forward-off-backward-off in a loop.
The issue is that only 4.79 volts (positive or negative) are being passed (measured no-load) irrespective of the rail voltage (tested at 10VDC and 19VDC)).
I am no doubt missing some important step, possibly some sort of biasing on the transistors? Or should I use a different spec darlington pair? (142s are way over the voltage requrements but were just what I had at hand, would using a 140 actually make any difference?).