The operational differences between thyristor-family and transistor family of devices

The operational differences between thyristor-family and transistor family of devices may now be summarised as under:

1. Once a thyristor is turned on by a gate signal, it remains latched in on-state due to internal regenerative action. However, a transistor must be given a continuous base signal to remain in on-state.
2. In order to turn-off a thyristor, a reverse voltage must be applied across its anode cathode terminals. However, a transistor turns off when its base signal is removed.
3. Turn-On and Turn-Off Mechanism: The most significant difference between thyristors and transistors is the way they turn on and off. Thyristors are latching devices, meaning that once they are turned on, they remain on until the current through them drops to zero. They require a minimum holding current to stay in the ON state. In contrast, transistors are non-latching devices, and they switch off when the current through them drops below a certain threshold.
4. Voltage and Current Ratings: Thyristors can handle much higher voltage and current ratings than transistors. This makes them more suitable for high power applications, such as motor control, lighting, and power supplies. Transistors are typically used in low-power applications, such as audio amplifiers, signal processing, and digital circuits.
5. Switching Speed: Thyristors have a slower switching speed than transistors. This is because thyristors have a relatively long turn-on and turn-off time, which limits their ability to switch rapidly. Transistors, on the other hand, have a much faster switching speed, making them suitable for high-frequency applications such as radio communication and switching power supplies.
6. Control: Thyristors require a trigger signal to turn on, which can come from a variety of sources, such as another electronic circuit or a mechanical switch. In contrast, transistors can be turned on and off directly by a control signal from a microcontroller, making them more flexible and easier to use in digital circuits.
7. Cost: Thyristors tend to be more expensive than transistors due to their high voltage and current handling capabilities. However, for high-power applications, thyristors can be more cost-effective than using multiple transistors in parallel.

The rating of a Silicon Controlled Rectifier (SCR) or thyristor typically includes the current rating of scr and anode voltage rating of scr