1. 8. 바이폴라 트랜지스터 (Bipolar Transistor)1

2. Bipolar Junction Transistors (BJTs)
Over the past 3 decades, the higher layout density and low-power advantage of CMOS technology has eroded away the BJT’s dominance in integrated-circuit products.
(higher circuit density  better system performance)
BJTs are still preferred in some digital-circuit and analog-circuit applications because of their high speed and superior gain.
faster circuit speed
larger power dissipation
 limits integration level to ~104 circuits/chip

3. 8-1. BJT 소자 공정
그림 8.1 BJT 소자공정 3

4. 8-2. 동작원리
용어정리
회로심볼 4

5. Common-emitter output characteristics
Modes of Operation
Common-emitter output characteristics
(IC vs. VCE)
Mode
Emitter Junction
Collector Junction
CUTOFF
reverse bias
Forward ACTIVE
forward bias
reverse bias*
Reverse ACTIVE
SATURATION
EE130 Lecture 23, Slide 5
*or not strongly forward biased

6. PNP BJT Operation (Qualitative)
“Active Bias”: VEB > 0 (forward bias), VCB < 0 (reverse bias)
ICn
“Emitter”
“Collector”
“Base”
ICp

7. BJT Performance Parameters (PNP)
Emitter Efficiency:
Decrease (5) relative to (1+2) to increase efficiency
Base Transport Factor:
Decrease (1) relative to (2) to increase transport factor
Common-Base d.c. Current Gain:
EE130 Lecture 23, Slide 7

8. Collector Current (PNP)
The collector current is comprised of
Holes injected from emitter,
which do not recombine in the base  (2)
Reverse saturation current of collector junction  (3)
where ICB0 is the collector current
which flows when IE = 0
Common-Emitter d.c. Current Gain:
EE130 Lecture 23, Slide 8

9. Performance parameters:
Emitter efficiency
Base transport factor
Common base d.c. current gain
Common emitter d.c. current gain
EE130 Lecture 23, Slide 9

10. BJT Design Important features of a good transistor:
Injected minority carriers do not recombine in the neutral base region
Emitter current is comprised almost entirely of carriers injected into the base (rather than carriers injected into the emitter

11. 그림 8.4 Common Base pnp BJT 특성
8-3. I-V 특성
이론(이상적인)으로 구한 I-V특성
그림 8.4 Common Base pnp BJT 특성 11

12. Measurement I-V

13. 8-3. 이론과 측정의 오차
Base width modulation
Geometrical effect 13

14. 8-3. Figure merit
그림 8.5
그림 8.6 14

15. Summary: BJT Performance Requirements
High gain (bdc >> 1)
One-sided emitter junction, so emitter efficiency g  1
Emitter doped much more heavily than base (NE >> NB)
Narrow base, so base transport factor aT  1
Quasi-neutral base width << minority-carrier diffusion length (W << LB)
IC determined only by IB (IC  function of VCE,VCB)
One-sided collector junction, so quasi-neutral base width W does not change drastically with changes in VCE (VCB)
Based doped more heavily than collector (NB > NC)
(W = WB – xnEB – xnCB for PNP BJT)

16. 8-5. 등가회로
그림 BJT 전류모델 16