Basic Electrical and Electronics Engineering: Unit III: Analog Electronics
SCR (Silicon Controlled Rectifier)
Construction, Operation, Characteristics, Basic Structure, Symbol
It is a four layer, three junction and three terminal device.
SCR-SILICON
CONTROLLED RECTIFIER CONSTRUCTION
It
is a four layer, three junction and three terminal device. The basic structure
and circuit symbol shown in fig.
P1
layer act as anode, N2 layer act as cathode and N1, P2
layer junction act as
Operation
SCR
is forward biased with a small voltage, it is in off and no current flows
through the SCR. If applied forward voltage is increased, one particular
voltage called forward breake over voltage and the junction J2 break
down. This causes the SCR switched to ON state
SCR
is reverse biased, then the junction J1 and J2 are
reverse biased and junction J2 is forward biased and most of the
voltage drop across junction J1 only. When the applied reverse
voltage is small, the SCR is OFF and there is no current flow through the
device.
Characteristics of SCR
There
are two types of V-I characteristics
(i)
Forward characteristics
(ii)
Reverse characteristics
Forward
characteristics.
Current
drawn between anode-cathode voltage (Vak) and anode current (IA)
at different gate current. The applied voltage across the SCR increases in
small suitable steps at each step
Reverse
characteristics
Reverse
characteristics is obtained by reversing the connections of the DC supplies.
Adjust the gate current to suitable value. Increase the reverse applied voltage
in suitable steps.
SCR
act as a switch when it is forward biased. When the gate is kept open IG
= 0. When IG<0, the amount of reverse biased applied to J2
is increased. So the break over voltage VBO is increased, when IG>0
the amount of reverse bias applied to J2 is decreased there by
decreasing the break voltage.
The
voltage at which SCR is switched ON can be controlled by varying the gate
current IG it is called as controlled switch.
Basic Electrical and Electronics Engineering: Unit III: Analog Electronics : Tag: : Construction, Operation, Characteristics, Basic Structure, Symbol - SCR (Silicon Controlled Rectifier)
Basic Electrical and Electronics Engineering: Unit III: Analog Electronics
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Basic Electrical and Electronics Engineering
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