High current TTL Driver Circuit


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HIGH is +5V and LOW is 0V unless specified otherwise.

The concept here is to drive heavier loads from a microcontroller I/O pin. Most are limited to 25-40mA This circuit can produce several amps.

High current TTL driver circuit.
Fig. 1

Fig. 1 circuit is non-inverting. HIGH in is HIGH out. LOW in is LOW out. When 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.

A load such as an LED 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 an LED connected between Y and +5V will turn on.



Sink current demo circuit.
Fig. 2 Sink current demo circuit.

Source current demo circuit.
Fig 3 Source current demo circuit.

High voltage buffer circuit using ULN2003 and pull up resistor.
Fig 4 High voltage buffer circuit using ULN2003 and pull up resistor.

High current TTL driver circuit with motor

Here I use two identical circuits each connected to one side of a DC motor. Two inputs 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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