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- Out of the three transistor connections, the common emitter circuit is the most efficient. It is used in about 90 to 95 per cent of all transistor applications. The main reasons for the widespread use of this circuit arrangement are:
(i) High current gain: In a common emitter connection, IC is the output current and IB is the input current. In this circuit arrangement, collector current is given by:
IC = ß IB + ICEO
As the value of ß is very large, therefore, the output current IC is much more than the input current IB. Hence, the current gain in CE arrangement is very high. It may range from 20 to 500.
(ii) High voltage and power gain: Due to high current gain, the common emitter circuit has the highest voltage and power gain of three transistor connections. This is the major reason for using the transistor in this circuit arrangement.
(iii) Moderate output to input impedance ratio: In a common emitter circuit, the ratio of output impedance to input impedance is small (about 50). This makes this circuit arrangement an ideal one for coupling between various transistor stages. However, in other connections, the ratio of output impedance to input impedance is very large and hence coupling becomes highly inefficient due to gross mismatching.
Wilfykil answered the question on August 15, 2019 at 05:45
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