JimDaldry.com

This is the schematic for one half of a motor drive. The motor is connected between the outputs of 2 of these circuits, and the inputs are cross-connected. When the input to R5 has more than about 1 and a half volts applied to it Q1 is driven into saturation and the output connection is raised to within a couple tenths of a volt of the supply voltage. If R8 is driven, Q2 is saturated and the output is within .2 volts of ground. Diodes D2 and D3 catch any reactive "kicks" from the motors. By using a grounded emitter output amplifier, I was able to get 11.6 volts across the motor with a 12 volt supply. If I had wired it as an emitter follower, the output would be about 10 volts. The inputs are easily driven by standard logic IC's.

The NPN transistors are 2N3904's, and the PNP's are 2N3906's. The diodes are 1N4002's. The transistors are prime parts from Dan's Small Parts. The resistors and diodes are from "grab bag" packages from the same source.

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