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EE130 Lecture 23, Slide 1Spring 2007
Lecture #23
QUIZ #3 Results (undergraduate scores only, N = 39)
Mean = 22.1; Median = 22; Std. Dev. = 1.995
High = 25; Low = 18
OUTLINE
The Bipolar Junction Transistor– Fundamentals– Ideal Transistor Analysis
Reading: Chapter 10, 11.1
EE130 Lecture 23, Slide 2Spring 2007
The base current consists of majority carriers supplied for1. Recombination of injected minority carriers in the base
2. Injection of carriers into the emitter
3. Reverse saturation current in collector junction• Reduces | IB |
4. Recombination in the base-emitter depletion region
Base Current Components (Active Bias)
EMITTER BASE COLLECTOR
p-type n-type p-type
EE130 Lecture 23, Slide 3Spring 2007
Circuit Configurations
Output Characteristics for Common-Emitter Configuration
EE130 Lecture 23, Slide 4Spring 2007
Modes of OperationCommon-emitter output characteristics
(IC vs. VCE)
Mode Emitter Junction Collector Junction
CUTOFF reverse bias reverse bias
Forward ACTIVE forward bias reverse bias*
Reverse ACTIVE reverse bias* forward bias
SATURATION forward bias forward bias
*or not strongly forward biased
EE130 Lecture 23, Slide 5Spring 2007
BJT Electrostatics• Under normal operating conditions, the BJT may be
viewed electrostatically as two independent pn junctions
EE130 Lecture 23, Slide 6Spring 2007
Electrostatic potential, V(x)
Electric field, (x)
Charge density, (x)
EE130 Lecture 23, Slide 7Spring 2007
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
Ep
CpT I
I
Tdc • Common-Base d.c. Current Gain:
EnEp
Ep
II
I
EE130 Lecture 23, Slide 8Spring 2007
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)