CLASSIFICATION OF AMPLIFIER ACCORDING TO FREQUENCY RESPONSE:-
Amplifiers can be classified based on the shape of their magnitude-response curve.Fig.shows typical frequency response curves for various amplifier types.
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| Frequency response for a capacitively coupled amplifier |
in above fig. the gain remains constant over a wide frequency range but falls off at low and high frequencies. This is a common type of frequency response found in audio amplifiers.
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| Frequency response for a direct-coupled amplifier |
IC amplifiers are usually designed as directly coupled or dc amplifiers (as opposed to capacitively coupled or ac amplifiers). Above Fig shows the frequency response of a dc amplifier. Such a frequency response characterizes what is referred to as a low-pass amplifier.
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| Frequency response for a tuned or bandpass amplifier |
In a number of applications, such as in the design of radio and TV receivers, the need
arises for an amplifier whose frequency response peaks around a certain frequency (called the center frequency) and falls off on both sides of this frequency, as shown in Fig. Amplifiers with such a response are called tuned amplifiers, bandpass amplifiers, or bandpass filters. A tuned amplifier forms the heart of the front-end or tuner of a communication receiver; by adjusting its center frequency to coincide with the frequency of a desired communications channel (e.g., a radio station), the signal of this particular channel can be received while those of other channels are attenuated or filtered out.
