Electronics Lecture 9: Thyristors

A four-layer pnpn device with an additional anode gate terminal. It can be turned on or off by applying a negative or positive pulse to the anode gate, respectively. It has faster turn-off time compared to SCRs.

Similar to the SCR, it has only three terminals but can be turned on and off by applying a pulse to the cathode gate. It offers faster switching speeds compared to SCRs and improved control.

A type of SCR that relies on light energy to trigger it into the conducting state. It has a sensitive silicon layer that responds to light, offering light sensing capabilities.

The Shockley diode is a two-terminal pnpn device that exhibits breakdown behavior. It operates in the "off" state until a specific voltage, called the breakover voltage (Vʙʀ), is reached, causing it to transition into the "on" state due to avalanche effects.

A two-terminal device composed of parallel-inverse pnpn layers. It can conduct current in either direction when the applied voltage exceeds a certain threshold, known as the breakover voltage (Vʙʀ₁ or Vʙʀ₂).

A three-terminal device based on a diac structure with an additional gate terminal. It can conduct current in both directions and can be turned on or off by a gate signal, similar to the SCR's control mechanism.

The ability of a four-layer pnpn device to maintain conduction even after the triggering pulse is removed. This occurs due to the regenerative process within the device's structure, where the collector current of one transistor reinforces the base current of the other, creating a self-sustaining loop.

The voltage at which a Shockley diode or diac transitions from the 'off' state to the 'on' state. This voltage, known as Vʙʀ, marks the threshold where the device enters the avalanche breakdown region and begins conducting.

The time it takes for a pnpn device to switch from the 'off' state to the 'on' state. This parameter is typically measured in microseconds (µs) and reflects the device's response time to a triggering signal.

The time it takes for a pnpn device to switch from the 'on' state to the 'off' state. This parameter is also measured in microseconds (µs) and indicates how fast the device can stop conducting after a triggering pulse is removed.

A simple application of the SCS as a voltage sensor. It uses the SCS's triggering characteristics to detect voltage levels and activate an alarm system or other circuits.

A circuit that uses the SCS to detect a change in a temperature-, light-, or radiation-sensitive resistor (Rₛ), triggering an alarm system when the resistance of Rₛ falls below a certain threshold.

A simple oscillator circuit using a GTO and a Zener diode to generate a sawtooth waveform. The GTO switches on and off, charging and discharging a capacitor, producing a rising and falling voltage pattern.

A circuit using a GTO to control the flow of current in a circuit controlled by varying the gate current. This can be done by using a resistor or other components to adjust the gate current level, which changes the conduction angle of the GTO and ultimately the amount of current flowing through the load.

Various circuits using LASCRs to detect and control light conditions. This can be used for applications like light switches, optical relays, and other photo-sensitive circuits.

An application of LASCRs as a latching relay, which offers isolation between the input and output. Light energy triggers the LASCR to allow current to flow through the load, acting as a latching or holding switch. A reset switch is often used to turn off the LASCR.

A circuit that uses a Shockley diode as a trigger switch for an SCR. The Shockley diode provides an initial trigger when its breakover voltage is exceeded, turning on the SCR.

A circuit employing a triac to control the flow of AC power to a load. The triac switches on and off during different portions of the AC signal, controlling the amount of power delivered to the load. Adjusting the triggering point can control the conduction angle of the triac, ultimately affecting the average power delivered to the load.

A transistor equivalent circuit representation of a four-layer pnpn device, such as an SCR, SCS, or GTO, showing the interconnected transistors that form the fundamental structure. It helps understand the internal workings of the device and its switching behavior.

Characteristic curves that describe the behavior of four-layer pnpn devices (SCR, SCS, GTO, etc.), showing the relationship between the applied voltage and the resulting current. These curves help understand the device's switching characteristics and are useful for determining operating points and designing circuits.

The property of a four-layer pnpn device that allows it to sustain a constant current flow even after the initial triggering pulse is removed. This is due to the regenerative feedback mechanism within the device structure, where the collector current of one transistor maintains the base current of the other.

The process of turning on a four-layer pnpn device, often achieved by applying a triggering pulse of sufficient magnitude to the gate terminal or by exceeding the breakover voltage, which triggers the device into the conducting state.

The process of stopping the conduction in a four-layer pnpn device, typically accomplished by reducing the anode current below the holding current value or by applying a turn-off pulse to the gate terminal, as seen in devices like the GTO and SCS.

Indicates that the current flow in a pnpn device is limited only by the external circuit. This is a typical characteristic of the device when in the 'on' state, effectively acting as a short circuit between the anode and cathode terminals.

Represents the behavior of a pnpn device in the non-conducting state, where it essentially acts as an open circuit, blocking the flow of current between the anode and cathode terminals.