Schmitt triggers are voltage comparators that have 2 threshold voltages that cause the output to change state. The middle ground voltages (hysteresis) keep the output in the last state that it was put into.

Digital Inverters give a high output when the input is low. Whereas the output goes low when the input is high. They are called NOT gates in digital electronics.

Don’t confuse a digital inverter with a power inverter takes in DC (usually from a battery) and outputs alternating current, usually at 120V.

The hysteresis of a schmitt trigger circuit prevents rapid repeated switching if the signal voltage is bouncing back and forth a tiny bit.

Brief circuit schematics with short video – List of pages

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Diagram:

Diagram is explained in the video below.

When pin 2 (trigger) has less than 1/3 supply voltage to it, the output goes high.

When pin 6 (threshold) gets more than 2/3 supply voltage, the output goes low.

From 1/3 to 2/3 supply voltage, the output stays in whatever state it was last put into. That’s the hysteresis range when using a 555 timer as a schmitt trigger.

Video:

Quick 555 timer based schmitt trigger inverting logic switch circuit schematic diagram to breadboard



555 timer pin layout:

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