BASE BIASED AMPLIFIERPREPARED BYKetan nayak (140413117005)Nirmal Gohil (140413117003)

INDEXSr No TITLE1 Introduction

2 Types of Amplifier

3 COMMON BASE AMPLIFIER

4 Circuit Diagram

5 Operation of a Common Base Amplifier

6 Features of the Common Base Amplifier

7 Characteristics of Common Base Amplifier

8 Applications of the Common Base Amplifier

INTRODUCTION• Amplifier:- An Amplifier, is an electronic device

that increase the power of a signal.

• It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude.

• In this sense, an amplifier modulates the output of the power supply to make the output signal stronger than the input signal.

TYPES OF AMPLIFIER• There are Basically Four Types of Amplifier.1. Voltage Amplifier2. Current Amplifier3. Transconductance4. Transresistance

• Common Base, Common Emitter and Common Collector are the Configurations of the Amplifier.

COMMON BASE AMPLIFIER• In electronics, a common base (also known as

grounded-base) amplifier is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a current buffer or voltage amplifier.

• In this circuit the emitter terminal of the transistor serves as the input, the collector the output, and the base is connected to ground, or "common", hence its name. The analogous field-effect transistor circuit is the common gate amplifier.

CIRCUIT DIAGRAM

OPERATION• In the Positive Half Cycle of Input Voltage Vs. Emitter

Voltage varies Sinusoidally above Q point value.• Hence Vbe reduces. This will reduce Ib which in turn

reduces Ic .• The Drop Across Rc .

i.e. IcRc will reduce and Collector Voltage Increase.• Thus we get a Positive half cycle of Output Voltage

corresponding to Positive Half Cycle of Input Voltage

• Similarly we get a Negative Half Cycle at the Outputcorresponding to the Negative half cycle at Input.

• Fig Shows the Input output Voltage Waveforms. Note that there is no Phase shift between input and Output of the Common Base Amplifier.

Features of Common Base Amplifier1. Input Signal Vs is applied at Emitter and amplified

output is taken at the collector w.r.t Ground.2. Base Terminal is Connected to Ground via

Capacitor C only for AC Signals.3. Input resistance of this configuration is very low,

hence source loading can take place.4. Output resistance is very Large.5. Current Gain is approximately equal to 1, so no

Current amplification is there.6. Voltage Gain is High.

CHARACTERISTICSCOMMON BASE AMPLIFIER CHARACTERISTICS

PARAMETER CHARACTERISTICS

Voltage gain High

Current gain Low

Power gain Low

Input / output phase relationship 0°

Input resistance Low

Output resistance High

APPLICATIONS• The Common Base Amplifiers are used for the

applications where impedance matching is to be achieved. They are also used as Wideband Amplifiers.

• i.e. The Amplifiers having Large Bandwidth.