Construct Common Base Amplifier and
Study its Characteristics
The schematic diagram is shown as follows:
Objective:
Construct Common Base Amplifier and
Study its Characteristics.
Apparatus:
Two DC power supplies, Function
Generator, AVO Meter, Oscilloscope, Transistors,
Resistors, and Capacitors.
Circuit Diagram:
Theory:
This is another type of Bipolar
Junction Transistor. This is referred to as the common
base mode because in this case, the base of the
transistor is common to the both input and output
terminals. The names are given to the modes due to
their unique set of characteristics observed for each
particular case. For the common base amplifier to
become
operational, the input voltage is applied across the
emitter and the output is taken from the collector. So Waveform :
one can rightly state that the emitter current is also the
input current and the collector current is the output
current. The base-emitter junction is forward biased.
The current gain namely alpha of approximate unity
but also a voltage gain that can also be very high with
typical values from 100 to 2000, which entirely
depends on the value of the collector resistance. We
know that the input impedance of the amplifier can be
very low but on the other hand, the output impedance
can be very high. We also extract from the
characteristics that it is entirely a non-inverting
phenomenon.
The amplifier current gain is given by:
The voltage gain is given by:
Procedure: Conclusion:
I constructed and verified the output of a
1. Construct the circuit on the breadboard common base amplifier. I reached the conclusion that
provided in the simulated lab of multisim, as indeed the experiment conveys the idea and the
shown in the figure. usefulness of this mode which in turn also opens the
2. All the transistors are to be placed correctly minds of young apprentices towards electronics.
and the connections made in accordance with
the circuit diagram, to make sure that the
circuit works just fine.
3. Apply the simulated power source.
4. Place the resistors at the required places.
5. Press F5 to run the simulation and verify the
truth table.
Advantages and Disadvantages:
By studying the characteristics we
can safely assume that there are some particular
advantages and disadvantages to using this mode of
the transistor. It has a high voltage gain, it also has a
low current gain and a low power gain. The input and
output signals are 0 degrees out of phase with respect
to each other. It has low input impedance and a
relatively high output impedance.
Applications:
1. It is used in moving coil microphone
amplifiers.
2. It is also used in UHF amplifiers.
3. These are also used in VHF amplifiers.
4. It is highly useful in audio and radio
frequency applications.
