THYRISTORS Flashcards
class of semiconductor devices characterized by 4-layers of alternating p and n materials. Four-layer devices act as either open or closed switches.
-THYRISTORS
It is a rectifier constructed of silicon material with a third terminal for control purposes.
-SILICON CONTROLLED RECTIFIER
resistance is typically 100 kOhms or more.
-REVERSE
resistance of the SCR is typically 0.01 to 0.1 ohm.
-DYNAMIC
SCR can be turned on by exceeding the forward breakover voltage or
-GATE CURRENT
Turning off SCR
- Anode current interruption
- Forced commutation
times of of SCRs are typically 0.1 to 1 microsecond.
-TURN ON
times of SCRs are typically 5 to 30 microsecond.
-TURN OFF
is that voltage above which the SCR enters the conduction region.
-FORWARD BREAKOVER VOLTAGE
is the value of gate current necessary to switch the SCR from the forward-blocking region to the forward conduction region under specified conditions.
-GATE TRIGGER CURRENT
is that value of current below which the SCR switches from the conduction state to the forward blocking region under stated conditions.
-HOLDING CURRENT
are the regions corresponding to the open circuit condition for the controlled rectifier which block the flow of charge (current) from anode to cathode.
-FORWARD AND REVERSE BLOCKING
is equivalent to the Zener or avalanche region of the fundamental two-layer semiconductor diode.
-REVERSE BREAKDOWN VOLTAGE
The characteristics of the device are essentially the same as those for the SCR.
-SILICON CONTROLLED SWITCH
can be used to turn the device either on or off.
-ANODE GATE CONNECTION
a negative pulse must be applied to the anode gate terminal.
-TURN ON THE DEVICE
while a positive pulse is required to
-TURN OFF THE DEVICE
An advantage of the SCS over a corresponding SCR is the
-REDUCED TURN OFF TIME
Turn off time is typically within the range 1 to 10 microseconds for the
-SILICON CONTROLLED SWITCH
Turn off time is typically 5 to 30 microseconds for the
-SILICON CONTROLLED RECTIFIER
The device is in the off state unit until the breakover voltage is reached, at which time avalance conditions develop and the device turnd on
Shockley diode
A gate terminal for controlling the the the turn on conditions of the bilateral device in either direction
Triac
Three terminal device with only one pn junction
Unijunction transistor
Four layer pnpn device with a gate connected directly to the sandwiched n type layer
Programmable unijunction transistor
