We believe that you have got a better understanding of this concept. This is all about different types of transistor configurations which includes common base, common collector and common emitter. Delta is used to specify a small changeįor instance, if the i/p current (IB) in a CE change from 50 mA to75 mA and the o/p current (IC) changes from 2.5mA to 3.6mA, the current gain (b) will be 44.įrom the above current gain, we can conclude that a change in base current generates a change in collector current which is 44 times larger. The current gain of the common emitter (CE) circuit is denoted with beta (β).It is the relationship between collector current and base current.The following formula is used to calculate the beta (β). The following table below shows the configurations of common emitter, common base and common collector transistors. In this kind of circuit, the emitter terminal is mutual to both i/p & o/p. The following diagram shows the configuration of CE transistor. This gives a good performance and it is frequently thought of as the most commonly used configurations. Emitter is heavily doped collector is moderately doped and base is lightly doped as we need most of the current from emitter should reach collector base current is needed only as a pilot signal for collector current variation. The gain of the both voltage and current can be defined as a medium, but the o/p is opposite to the i/p that is 1800 change in the phase. The circuit of CE transistor gives a medium i/p and o/p impedance levels. The common emitter transistor configuration is most widely used configuration. If we want to use the same transistor in a CC, we can calculate gamma by the following equation.Ĭommon Emitter Transistor Configuration (CE) Therefore, a variation in base current of this transistor will give a change in collector current that will be nine times as big. These relations are given below.įor instance, the current gain value of the common base value (α) is 0.90, then the beta value can be calculated as When the transistor is connected in any of three basic configurations such as CE, CB and CC then there is a relationship between alpha, beta and gamma. This gain is related to CB current gain that is beta (β), and gain of the CC circuit is calculated when the b value is given by the following formula The current gain of the CC circuit is denoted with (γ) and it is calculated by using the following formula. Common Collector Transistor Configuration The collector terminal is mutual to both i/p and o/p circuits. The following diagram shows the configuration of CC transistor. Offering a high i/p impedance & a low o/p impedance are commonly used as a buffer.The voltage gain of this transistor is unity, the current gain is high and the o/p signals are in phase. The common collector transistor configuration is also known as the emitter follower because the emitter voltage of this transistor follows the base terminal of the transistor. Common Collector Transistor Configuration (CC)
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