A- Introduction B.J.T B- Position of the terminals and symbol of B.J.T C- Common-Base Configuration D- Circuit Arrangement For Input and Output Characteristic Curve in CB Configuration E- Transistor Characteristics in Common-Base Configuration

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