/diy/ - Do It Yourself

>>1273448
If you search for 'half bridge' you will find a lot, I left off the space. It's one half of a full bridge usually called H-bridge because the circuit looks like the letter H. It runs on a single supply rather than a split (±) supply. The motor can still be reversed but now you need a linear dual (stereo) pot and it must be wired such that while one side goes up the other goes down and vice versa. The picture shows how. The 4 diodes are only for protection of the transistors and can be left off for small supply voltages. 4.5V for a 3V motor should work because you now lose 1.4V compared to 0.7V on the half bridge.

Combining two transistors to increase the current gain is usually called a Darlington configuration and this is a complementary (NPN/PNP) version of it which behaves almost like a single transistor with high current gain.