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Questions and Answers
What is the minimum parameter at which a Silicon Unilateral Switch (SUS) starts conducting heavily?
What is the minimum parameter at which a Silicon Unilateral Switch (SUS) starts conducting heavily?
What is the minimum anode current required to maintain the SUS in the on state?
What is the minimum anode current required to maintain the SUS in the on state?
What happens when the anode current IA drops below the holding current IH value in an SUS?
What happens when the anode current IA drops below the holding current IH value in an SUS?
What is the effect of dv/dt triggering on the inner junction of an SUS?
What is the effect of dv/dt triggering on the inner junction of an SUS?
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What is the term for the value of the anode current at the point where the SUS changes from the forward-blocking region to the forward-conducting region?
What is the term for the value of the anode current at the point where the SUS changes from the forward-blocking region to the forward-conducting region?
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Study Notes
Thyristors
- Thyristors are constructed using four semiconductor layers (pnpn).
- They include devices such as the 4-layer diode, SCR, diac, triac, SCS, and others.
- Thyristors act as open circuits, capable of withstanding a certain rated voltage until triggered.
- Once triggered, they turn on and become low-resistance current paths, remaining so until the current is reduced to a certain level or until they are triggered off.
Four Layer Diode (Shockley Diode or Silicon Unilateral Switch)
- A type of thyristor constructed from four semiconductor layers.
- SUS Operation:
- Breakover Voltage: minimum forward voltage at which the SUS starts conducting heavily.
- Holding Current: minimum anode current required to maintain the SUS in the on state.
- Switching Current: the value of the anode current at the point where the SUS changes from the forward-blocking region to the forward-conducting region.
Firing an SUS
- Two methods to fire an SUS:
- Supplying a voltage in excess of its breakover voltage.
- Excessive voltage rise in the bias voltage VAK or dv/dt triggering.
- When VAK surpasses the breakover voltage, the SUS saturates and enters the conduction stage.
- The SUS will remain on unless the anode current IA drops below the holding current IH value.
dv/dt Triggering
- At forward-blocking region, the two outer junctions (1 & 3) are forward biased, but the inner junction (2) is reverse biased.
- The reverse-biased junction 2 behaves like a capacitor due to the space-charge present.
- A current will flow in the device to charge the device capacitance.
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Description
This quiz covers the basics of thyristors, including their construction, types, and functionality. Learn about the characteristics and uses of thyristors in electronics.
