Triggers can often be found in electronic circuits. They participate in the work of many nodes, performing a variety of tasks, or can be implemented on different elements, but the principle of their work remains the same. A special case is the so-called Schmitt trigger, well-established in the work. This useful modification of the original scheme in a short time has gained immense popularity among designers.
There are a variety of options for implementing this idea: a trigger on transistors, operational amplifiers, digital microcircuits, etc. As an example, you can consider a digital Schmitt trigger, the principle of which will help us in general to deal with this device. Suppose that we have developed a circuit that has two inputs and two outputs. With a combination of input signals 0-1 or 1-0, the output state changes. With all other options, such a device will remember its original state. It would seem, and here is the Schmitt trigger and what is his idea?
After the invention of the comparator, a device with input limitation and an infinite coefficient, the idea arose to create small devices that would be able to memorize the original combination. The first was the Schmitt trigger on the comparator. A major drawback of this scheme was the drift of the signal in the triggering region The trigger itself. This shortcoming was eliminated by Schmitt after introducing the hysteresis into the operation of the circuit. In this case, when a certain level of operation of the device has been exceeded, it switched over, but it was possible to return to the initial state only under the condition of reverse switching. In other words, the introduction of a hysteresis into the operation of the circuit led to its stable operation. The "bounce" at the output stopped, it became inertial and, in connection with this, reliable in operation. This device was called the Schmitt trigger and bears the name of its creator.
The operation of the digital device described above fully meets these requirements. It has a certain trigger threshold. There are voltage levels for each of the states - "zero" and "one". This is the ideal Schmitt trigger. If you enter a small switch delay, you can get rid of most of the interference that often occurs with many devices.
The field of application of such devices is quite extensive: they monitor the condition of the sensors, they are used in burglar alarms, automated systems in the workplace, while operating circuits of electronics for a variety of purposes. Probably, many of us included slot machines using tokens? To prevent the jitter of the contacts of the microswitch when the medal passes through the coin changer, a Schmitt trigger is installed in the circuit. It ensures the stable operation of the entire gaming machine.
With the development of the element base and the technology of manufacturing of electronic devices, there is a steady tendency to miniaturize the triggers and improve their performance characteristics.