SAGAR INSTITUTE OF RESEARCH &TECHNOLOGY,BHOPAL

Synopsis on common base transistor characteristics

Submitted by:-

Manish kumar

INDEX1. OBJECTIVE

2. INTRODUCTION

3. THEORY

4. CIRCUIT DIAGRAM

5. COMPONENT USED

6. COMPONENT SPECIFICATION & DATA SHEET

1.OBJECTIVE:- To design the

electronic circuit in common base configuration & study its characteristics

2.INTRODUCTION:- Bipolar transistors are so named

because the controlled current must go through two types of semiconductor material: P and N. The current consists of both electron and hole flow, in different parts of the transistor.

Bipolar transistors consist of either a P-N-P or an N-P-N semiconductor “sandwich” structure.

The three leads of a bipolar transistor are called the Emitter, Base, and Collector.

• Transistors function as current regulators by allowing a small current

to control a larger current. The amount of current allowed b/w collector and emitter is primarily determined by the amount of current moving between base and emitter.• In order for a transistor to properly function as a current regulator, the controlling (base) current and the controlled(collector)currents must be going in the proper directions:meshing additively at the emitter and going against the emitter arrow symbol.

.The transistors can be connected in the following three different configurations.

1. Common base configuration

2. Common collector configuration

3. Common emitter configuration

3.THEORY:-

Transistor operation The emitter-base junction is forward

biased

The base-collector junction is reverse biased

Currents in a transistor

Emitter current is sum of the collector and base currents:

IE =IC+IB

The collector current is comprised of two currents

Common-Base Configuration

The base is common to both input (emitter–base) and

output (collector–base) of the transistor.

Common-Base Amplifier

Input Characteristics

This curve shows the relationship between of input current (IE) to input voltage (VBE) for three output voltage (VCB) levels.

Output Characteristics

This graph demonstrates the output current (IC) to an output voltage (VCB) for various levels of input current (IE).

Operating Regions

Active – Operating range of the amplifier.

Cutoff – The amplifier is basically off. There is voltage, but little current.

Saturation – The amplifier is full on. There is current, but little voltage.

Approximations

Emitter and collector currents:-

Base-emitter voltage:-

Current amplification factor:-

Alpha (α):- ratio of IC to IE

EI

CIα dc

Ideally:- α = 1In reality: a is between 0.9 and 0.998

Alpha () in the AC mode:-

EI

CIαΔ

Δac

4.CIRCUIT DIAGRAM :-

5.COMPONENT USED :-1. Resistor

2. Capacitor

3. Transistor

7. COMPONENT SPECIFICATION & DATA SHEET :-