I am getting started with electronics and decided to learn about the inner workings of the L293D. However, I found a symbol I don't recognize, which is the triangle with 3 connections. There are four of them in the schematic.

At first I thought they were op amps, but those have 5 inputs.

Here is the L193 diagram



1 Answer 1


They are drivers with enables. Basically they take low-current drive signals (from a microcontroller, for example) and amplify them to high-current capable of driving high-power devices, in this case motors. The wire going into the "back" of the triangle is the input signal, the wire coming out of the "front" of the triangle is the output drive, and the wire going into the "side" of the triangle is an enable input, turning the driver on or off.

  • \$\begingroup\$ Do the symbols next to the pins which represent a square wave with 0 or 1 signaled have anything to do with the amplifier? If they have, why are the 9 and 10 pin symbol different? \$\endgroup\$ May 13, 2018 at 14:37
  • \$\begingroup\$ They're example waveforms of the signals found on those pins. The enable line on Pin 9, for example, is active when it goes from low to high. The control signal on Pin 10, for example, is active when it oscillates between high to low to high.... (repeated square wave). \$\endgroup\$
    – DerStrom8
    May 13, 2018 at 14:51

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