Engineering Projects

Amplifiers may be classified or Classification of Amplifiers in several ways as described below: According to the Frequency Range | Classification of Amplifiers Thus amplifiers may be classified as below: DC (Direct coupled) Amplifiers from zero frequency (dc) onwards. Audio Frequency Amplifiers 20 Hz to 20 KHz Video Frequency Amplifiers up-to a few MHz. Radio Frequency (RF) Amplifiers from a few KHz to hundreds of MHz. Ultra-high Frequency (UHF) and Microwave Amplifier up-to hundred or thousands of MHz. According to the method of operation | Classification of Amplifiers The position of the…

Approximate h-model: In the analysis of the transistor amplifier, we have as far used the exact h-model for the transistor. In practice, we may conveniently use an approximately h-model for the transistor which introduces an error of < 10% in most cases. This much error may be conveniently tolerated since the h-parameters themselves are not steady but vary considerably for the same type of transistor. We first derive this approximate CE h-model. Figure 1 gives the equivalent circuit of the CE amplifier using the exact h-model for the CE transistor.…

Comparison of CE, CB and CC Configurations: It is useful to study the variation of AI, AV and Ri with change in load resistance RL for each of the three configurations. Similarly, we may study variation of R0 with change of source resistance RS. Figure 1, 2 and 3 plots for each of the three configurations, current gain AI, voltage gain AV and input resistance Ri respectively as function of load resistance RL for the typically transistor whose h-parameters are given in Table 4.1. From these curves we get the…

Common Collector Amplifier or the Emitter Follower: Figure 1(a) gives the basic circuit of a common collector amplifier, popularly called emitter follower. Its voltage gain is close to unity (one) and, therefore, any increment in the input voltage i.e. the base voltage appears as an equal increment in the output voltage across the load resistor in the emitter circuit. Thus, the emitter may be said to follow the input signal and hence the name emitter follower. The input resistance Ri of a CC amplifier or emitter follower is very high,…

Analysis of Common Base Amplifier (CB) using h-parameter: Figure 1 gives the basic circuit of a transistor (NPN type) used as a common base (CB) amplifier. In this case, Vs is the signal voltage, Vi is the actual voltage at the input terminals and V0 is the output voltage. Figure 2(a) gives the a.c. equivalent circuit obtained on having removed the dc source. On replacing the CB transistor with its small-signal two generator h-parameter model we get the equivalent circuit of figure 1(b). Here also we assume sinusoidal input. Hence…