6. 12/27/2020 Arpan Deyasi, RCCIIT 6
Q1
Q2
IA
IEP
IBP
ICP
IBN
IA
ICN
IEN
IA: Anode current
or total current
Current components in Equivalent Circuit
7. 12/27/2020 Arpan Deyasi, RCCIIT 7
For any BJT
C E COI I Iα= +
CN N EN CONI I Iα= +
CP P EP COPI I Iα= +Q1:
Q2:
Analysis
8. 12/27/2020 Arpan Deyasi, RCCIIT 8
IA
IEP
IBP
ICP
IBN
Q1
Q2
IA
ICN
IEN
CP P EP COPI I Iα= +
Analysis
EP BP P EP COPI I I Iα− = +
EP P EP COP BPI I I Iα= + +
9. 12/27/2020 Arpan Deyasi, RCCIIT 9
A EPI I=
IA
IEP
IBP
ICP
IBN
Q1
Q2
IA
ICN
IEN
Analysis
EP P EP COP BPI I I Iα= + +
A P A COP BPI I I Iα= + +
(1 )A P COP BPI I Iα− = +
10. 12/27/2020 Arpan Deyasi, RCCIIT 10
Analysis
IA
IEP
IBP
ICP
IBN
Q1
Q2
IA
ICN
IEN
BP CNI I=
(1 )A P COP BPI I Iα− = +
(1 )A P COP CNI I Iα− = +
(1 )A P COP N EN CONI I I Iα α− = + +
11. 12/27/2020 Arpan Deyasi, RCCIIT 11
Analysis
EN AI I=
IA
IEP
IBP
ICP
IBN
Q1
Q2
IA
ICN
IEN
(1 )A P COP
N EN CON
I I
I I
α
α
− = +
+
(1 )A P COP N A CONI I I Iα α− = + +
12. 12/27/2020 Arpan Deyasi, RCCIIT 12
Analysis IA
IEP
IBP
ICP
IBN
Q1
Q2
IA
ICN
IEN
(1 )A P N
COP CON
I
I I
α α− −
= +
(1 )A P N COI Iα α− − =
(1 )
CO
A
P N
I
I
α α
=
− −
13. 12/27/2020 Arpan Deyasi, RCCIIT 13
Analysis
(1 )
CO
A
P N
I
I
α α
=
− −
low supply condition ( ) 1P Nα α+ <<
Forward blocking state / OFF state
A COI I≈
14. 12/27/2020 Arpan Deyasi, RCCIIT 14
Analysis
(1 )
CO
A
P N
I
I
α α
=
− −
low supply condition ( ) 1P Nα α+ <<
Forward blocking state / OFF state
A COI I≈
15. 12/27/2020 Arpan Deyasi, RCCIIT 15
Analysis
(1 )
CO
A
P N
I
I
α α
=
− −
high supply condition ( ) 1P Nα α+
Forward breakdown state / ON state
AI ∞
16. 12/27/2020 Arpan Deyasi, RCCIIT 16
I-V characteristics of Shockley Diode
VAKFVAKR
IAF
IAR
Diode region
Unstable region
Reverse
bias region
VBR
ICO
0.7 V
IL
IH
17. 12/27/2020 Arpan Deyasi, RCCIIT 17
Drawbacks of Shockley Diode
Electrical length of unstable region is very long
Q: How to reduce it?
VBR should be lowered
Solution: Shockley diode with additional bias
18. 12/27/2020 Arpan Deyasi, RCCIIT 18
I-V characteristics of Shockley Diode
VAKFVAKR
IAF
IAR
Unstable region
VBR
0.7 V
(VJ1+VJ3-VJ2) < 2.1 V
19. 12/27/2020 Arpan Deyasi, RCCIIT 19
Modified Shockley Diode
p n p n
J1 J2 J3
Silicon
Controlled
Rectifier
20. 12/27/2020 Arpan Deyasi, RCCIIT 20
I-V characteristics of SCR
VAKFVAKR
IAF
IAR
Unstable region
VBR
0.7 V
VBR1
VBR2VBR3