The document details the input and output characteristics of bipolar junction transistors (BJTs), covering their basic configuration, terminal positions, and the distinction between PNP and NPN types. It explains the input and output characteristics in common-base configuration, highlighting the regions: active, cutoff, and saturation, as well as concepts like knee voltage and dynamic resistances. Overall, it serves as a foundational overview of BJTs used as amplifiers and switches in electronic systems.

1. BJT Input and Output
Characteristics(C-B)

2. Contents:
• Introduction
• Position of the terminals and symbol
of BJT
• Common-Base Configuration
• Transistor Characteristics in
Common-Base Configuration

3. Introduction
• The basic of electronic system nowadays is
semiconductor device.
• The famous and commonly use of this device
is BJTs
(Bipolar Junction Transistors).
• It can be use as amplifier and logic switches.
• BJT consists of three terminal:
 collector : C
 base : B
emitter : E
• Two types of BJT : pnp and npn

4. Position of the terminals and symbol of
BJT
• Base is located at the middle
and more thin from the level
of collector and emitter
• The emitter and collector
terminals are made of the
same type of semiconductor
material, while the base of the
other type of material

5. Transistor Characteristics in Common-
Base Configuration
In common-base configuration 2 types of characteristics are :
1. Input Characteristics :
Curves relate the input or emitter current IE and input or emitter-to-
base voltage VEB keeping output or collector-to-base voltage VCB
constant.
2. Output Characteristics :
Curves relate the output or collector current IC and output or
collector-to-base voltage VCB keeping the input or emitter current
IE constant.

6. Circuit Arrangement For Input and Output Characteristic Curve in CB Configuration

7. Transistor Input Characteristics in
Common-Base Configuration

8. • The cut-in voltage or knee voltage the emitter current is
negligibly small.
• After the knee-voltage , the emitter current IE increases
rapidly with a small increase in the emitter-to-base
voltage VEB. This indicates that input resistance is very
small.
• With the increase in VCB ,the curve shifts upwards or
becomes vertical. Hence ri decreases .
• At any point on the curve , the value of a.c. or dynamic input
reistance is given as
ri = (VEB / IE) | VCB Constant

9. Output Characteristics in Common-
Base Configuration

10. • The output characteristics has 3 basic regions:
- Active region
- Cutoff region
- Saturation region
• In active region, the collector current IC is approximately equal to the
emitter current IE .
• Emitter Current increases slowly for increase in VCB in active region .
Hence in Active region , curves are nearly flat. This also means that
output resistance in this configuration is very large .
• If VCB becomes negative, the collector-base junction is set in
forward biased which causes collector current to decrease rapidly .
This region is known as Saturation region, in saturation region Ic
does not depend much on emitter current .
• In saturation region, since the collector-base junction is also forward
biased , a small increase in VCB results in a large increase in
collector current .

11. • If emitter current IE made zero, then the collector current
is not zero. It has a small value. This small value is
leakage current ICBO. The curve for IE = 0 corresponds to
cut-off region.
• At any point on the curve , the value of dynamic output
resistance is given as
ro = (VCB / IC) | IE =Constant

12. References:
• Google
• Dr. Sanjay Sharma