3. Forward Blocking StateForward Blocking State
High voltage low
current mode.
SCR is in “OFF” state.
The current is called
“Forward Leakage
Current” which flows
due to minority
carriers.
4. Transition StateTransition State
As long asVAK <VBO SCR remains
in blocking state.
As soon asVAK >VBO,the anode
current ia increases sharply to
a high value.
The voltage across SCR
reduces sharply to a low
value/state voltage.
This switching of SCR from
OFF to ON state and vice
versa takes place in short time.
It is an unstable state.
5. ON StateON State
The voltage across
SCR is low.
Average current in
this state is as large
as 2000 A with ON
state voltage drop
of few volts.
6. Similar to the reverse biased
DIODE.
For VAK <VBR, a very small
leakage current flows through
the SCR.
But as soon as VAK reaches VBR,
the avalanche breakdown
occurs and a large reverse
current flows.
It can damage the SCR, so
operation in this mode should
be avoided.
