Technology Remaking the World

High current TTL Driver Circuit

by Lewis Loflin

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The concept here is to drive heavier loads from a micro-controller IO pin. Most are limited to 40mA, this can produce several amps.

High current TTL driver circuit.

The circuit is non-inverting. HIGH in is HIGH out. LOW in is LOW out. When the DIN is HIGH the output of the 7404 goes LOW. This turns on Q1 a P-channel MOSFET power transistor, turns off Q2 a N-channel MOSFET. This is the current "source" mode.

A load such as a motor connected between Y and ground would turn on.

If DIN is LOW The output of the 7404 goes HIGH. Q1 is turned off, Q2 is turned on. This is the "sink" mode. A load such as a motor connected between Y and +Vcc will turn on.

High current TTL driver circuit with motor

Here I use two identical circuits each connected to one side of a DC motor. Two input can forward or reverse the motor rotation. Note the truth table. Only when the inputs A and B differ does the motor operate.

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