amplifier teransistor

1. Source
Drain
Gate
Dam
Valve
ArteryVein
Heart

2. Gain medium
Incoherent
Light
Coherent
Light
ECE 663
Source
Drain
Gate
Valve
ArteryVein
Emitter Collector
Base
Ion Channel
Dam Laser Heart
Axonal conductionMOSFETBJT

3. • Output current can toggle between large and small
(Switching  Digital logic; create 0s and 1s)
• Small change in ‘valve’ (3rd
terminal) creates Large
change in output between 1st
and 2nd
terminal
(Amplification  Analog applications; Turn 0.5  50)

4. Gain = 300

5. http://www.computerhistory.org/semiconductor/timeline.html#1940s

6. • How can we get ‘Gain’?
• What is the structure of the device to get gain?
• What is the equation for gain?
• How can we use this equation to maximize gain?
• How can we model this device as a circuit element?
• What are its AC characteristics and speed?

7. P N
W
Vappl > 0
-+
N P
W
Vappl < 0
-+
Forward bias, + on P, - on N
(Shrink W, Vbi)
Allow holes to jump over barrier
into N region as minority carriers
Reverse bias, + on N, - on P
(Expand W, Vbi)
Remove holes and electrons away
from depletion region
I
V
I
V

8. P N
W
Vappl > 0
-+
N P
W
Vappl < 0
-+
Holes from P region (“Emitter”) of 1st
PN junction
driven by FB of 1st
PN junction into central N region (“Base”)
Driven by RB of 2nd
PN junction from Base into P region of
2nd
junction (“Collector”)
• 1st
region FB, 2nd
RB
• If we want to worry about holes alone, need P+ on 1st
region
• For holes to be removed by collector, base region must be thin

9. +
- +
-
IE
IB
IC
IE = IB + IC ………(KCL)
VEC = VEB + VBC ……… (KVL)

10. ECE 663
GAIN
CONFIG

11. +
- +
-
IE
IB
IC
ECE 663
VEB, VBC > 0  VEC >> 0
IE, IC > 0  IB > 0
VEB >-VBC > 0  VEC > 0 but small
IE > -IC > 0  IB > 0
VEB < 0, VBC > 0  VEC > 0
IE < 0, IC > 0  IB > 0 but small

12. ECE 663
Bias Mode E-B Junction C-B Junction
Saturation Forward Forward
Active Forward Reverse
Inverted Reverse Forward
Cutoff Reverse Reverse

13. ECE 663

14. ECE 663
PNP BJT Electrostatics

15. ECE 663
PNP BJT Electrostatics

16. ECE 663

17. ECE 663
Most holes
diffuse to
collector
Large injection
of Holes
Collector Fields drive holes
far away where they can’t
return thermionically
Few recombine
in the base
VEB > 0
VCB > 0

18. ECE 663