Triggers can often be found in electronic circuits. They participate in the work of many nodes, performing a wide 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, which has proven itself in work. This useful modification of the original circuit in a short time gained immense popularity among designers.
There are a variety of options for implementing this idea: a trigger on transistors,
operational amplifiers, digital circuits, etc. As an example, consider the Schmitt digital trigger, the principle of which will help us in general to deal with this device. Suppose we have developed a circuit that has two inputs and two outputs. With a combination of input signals 0-1 or 1-0, the state of the output will change. With all other options, such a device will remember its original state. It would seem, where does Schmitt’s trigger come in, and what is his idea?
After the invention of the comparator, a device with an input signal limitation and an infinite coefficient, the idea came up to create small devices that would be able to memorize the original combination. The first Schmitt trigger was assembled on a comparator. The drift of the signal in the triggered area was considered a major drawback of such a circuit
trigger itself. This shortcoming was eliminated by Schmitt after the introduction of hysteresis in the operation of the circuit. In this case, when a certain level of operation of the device was exceeded, it switched, but it was possible to return to its original state only under the condition of reverse switching. In other words, the introduction of hysteresis into the operation of the circuit led to its stable operation. The “bounce” at the exit ceased, it became inertial and therefore reliable in operation. Such a device is called a Schmitt trigger and bears the name of its creator.
The operation of the digital device described above fully meets these requirements. He has a certain threshold. There are voltage levels for each of the states - “zero” and “one”. This is Schmitt's perfect trigger. If you introduce a small delay on switching, you can get rid of most of the interference that often occurs when many devices.
The scope of such devices is quite extensive: they monitor the status of sensors, are used in burglar alarms, automated systems in production, and when working with electronic circuits for various purposes. Probably many of us turned on slot machines using tokens? To prevent the contact bounce of the micro switch when the token passes through the coin acceptor, the 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 electronic devices, there is a steady tendency towards miniaturization of triggers and an improvement in their operational characteristics.