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Home Electrical and Electronics Analog Electronics To Study the Characteristics of Transistor in Common Base Configuration
Analog Electronics Lab Experiments

To Study the Characteristics of Transistor in Common Base Configuration



Aim

To Study the characteristics of transistor in Common Base configuration.

Apparatus Required:

Power supply, Transistor characteristics Kit, Connecting Leads, Voltmeter, Ammeter.

Brief Theory:

Transistor is a semiconductor device consist of two p-n junctions. It has three terminals, to handle I/P and O/P four terminals are needed. Therefore, one terminal is made common. A transistor can be connected in three Ways CB, CE, and CC.

Common base: Base is made common. I/P is connected between base & emitter and O/P is taken between base & collector.

Input charact.The curve plotted between emitter current I & the emitter-base voltage constant collector-base voltage V.

Output charact.The curve plotted between collector current I & collector-base voltage V constant emitter current I.

Circuit Diagram:

circuit-diagram

Procedure:

Input charact.

  1. Make the connection as per circuit diagram .
  2. Switch ‘ON’ the supply & set V = 0V
  3. Vary V in step & note down the emitter current I at each step .
  4. Set V = 1V & again repeat the same procedure .
  5. Draw the graph.

Output charact.

  1. Make the connection as per circuit diagram.
  2. Set the value of I = 1mA
  3. Vary V in step & note down the collector current I at each step.
  4. Set I = 2mA & repeat the same procedure.
  5. Draw the graph.

Observation Table:

S. No Input charact.(Vcb=Cons.)/Ie(mA)/Veb(Volts) Output charact. (Ie = Const.)/Ic(mA)/Vcb(Volts)
1
2
3
4
5

Graph:

input-output-characteristics

Result:The input and output characteristics of transformer in CB configuration has been plotted.

Discussion:With the help of output characteristics we can calculate ac & dc current gain in CB configuration.

Precautions:

  1. Always connect the voltmeter in parallel & ammeter in series as shown in fig.
  2. Connection should be proper & tight.
  3. Switch ‘ON’ the supply after completing the ckt.
  4. DC supply should be increased slowly in steps
  5. Reading of voltmeter & Ammeter should be accurate.

Quiz:

Q1:What do you mean by biasing of transistor?

A1:When dc voltages are applied across the different terminals of transistor, it is called biasing.

Q2:What is d.c. current gain in common base configuration?

A2:It is ratio of collector current(Ic) to emitter current (Ie).

Q3:What is typical value for d.c. current gain ?

A3:0.99

Q4:What is a.c. current gain in CB confifuration?

A4:It is ratio of change in collector current to change in emitter current.

Q5:What are input characteristics?

A5:These curves relate i/p current & i/p voltage for a given value of o/p voltage.

Q6:What are output characteristics?

A6:These curves relate o/p voltage & o/p current for a given value of input current.

Q7:Which configuration has highest voltage gain?

A7:Common Emitter.

Q8:Which configuration is most widely used?

A8:Common Emitter.

Q9:What is operating point?

A9:The zero signal values of Ic & Vce.

Q10:Which reigon is heavily doped in Transistot?

A10:Emitter