The emitter base junction is forward biased by V EE and collector base junction is reverse biased by V CC. The common emitter amplifier circuit using NPN transistor is as shown below, the input signal being applied at emitter base junction and the output signal being taken from collector base junction. The amplifier circuit that is formed using a CE configured transistor combination is called as CE amplifier. Hence CB configured amplifiers are used at high frequency applications. The voltage gain is also low compared to CE configuration. If CB configuration is considered for amplification, it has low input impedance and high output impedance. So, there is no phase reversal between input and output in a CB amplifier. In CB configuration, a positive input produces a positive output and hence input and output are in phase. Thus, a positive half cycle output is produced. The below figure shows the CB amplifier with self-bias circuit.īoth the collector current and emitter current get decreased.Īs I CR C decreases, V CB increases. As a result of this, the base current I B also gets decreased. As V be is at negative with respect to ground, the forward bias is decreased, for the positive half of the input signal. When no input is applied, the quiescent conditions are formed and no output is present. Thus the values of I c, I b and I cb are decided by V CC, V EE, R e and R c. The operating point is adjusted with the help of resistors Re and R c. The common base amplifier circuit using NPN transistor is as shown below, the input signal being applied at emitter base junction and the output signal being taken from collector base junction. The amplifier circuit that is formed using a CB configured transistor combination is called as CB amplifier. Let us now study different configurations to understand which configuration suits better for a transistor to work as an amplifier. The voltage gain and power gain should also be high to produce a better output. For an amplifier it is a better state to have a high input impedance, in order to avoid loading effect in Multi-stage circuits and lower output impedance, in order to deliver maximum output to the load. Emitter Follower & Darlington AmplifierĪny transistor amplifier, uses a transistor to amplify the signals which is connected in one of the three configurations.Transformer Coupled Class A Power Amplifier.
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