The block diagram of the current series feedback-amplifier is shown below, by which it is apparent that the feedback circuit is located in series by means of the output as well as the input.
The block diagram of the current shunt feedback-amplifier is shown below, by which it is apparent that the feedback circuit is located in shunt by means of the output as well as the input. The amplifier characteristics which are affected by various negative feedback are listed in the following table.
Current Series Increases. Thus, this is all about feedback amplifier, types, and topologies. Due to these drawbacks, this kind of feedback is not suggested for the amplifiers.
So, when the positive feedback is adequately large, then it directs to oscillations. Both the input signal and feedback signal introduces a phase shift of o thus making a o resultant phase shift around the loop, to be finally in phase with the input signal.
Though the positive feedback increases the gain of the amplifier, it has the disadvantages such as. It is because of these disadvantages the positive feedback is not recommended for the amplifiers. If the positive feedback is sufficiently large, it leads to oscillations, by which oscillator circuits are formed. In negative feedback, the amplifier introduces a phase shift of o into the circuit while the feedback network is so designed that it produces no phase shift or zero phase shift.
Thus the resultant feedback voltage V f is o out of phase with the input signal V in. Though the gain of negative feedback amplifier is reduced , there are many advantages of negative feedback such as. Hence, by decreasing the gain the stability of the system increases and vice-versa. So to have a stable system, the gain of the amplifier must be small and it is achieved by employing negative feedback in the circuit.
Let us now discuss the case where no any feedback network is employed in the amplifier circuit but feedback is provided in the circuit by some physical connection. As we can see in the diagram shown below-. So, for positive feedback amplifier. And in case of the negative feedback amplifier. Hence we can say that the gain of an amplifier depends on the type of feedback employed in the circuit. From the above discussion, we can conclude that a negative feedback is much better than positive feedback.
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This is referred to as the positive type. It is also known as a direct amplifier. But these kinds of amplifiers are not good at amplification but can be used in the various types of oscillators. The feedback signal applied to the amplifier if its input signal decreases because of its application. The applied input can be of voltage or current signals.
This type of feedback is known as a negative type. It is also referred to as an inverse amplifier. In this case, the noise generated in the circuit is reduced. Hence, it is most widely used in the amplification of the signals. In the feedback amplification of the signals, either the voltage or the current signals can be applied at the input of the amplifiers. Hence the topologies that are known for its series and the shunt characteristics are applied for both the voltage and the current signals.
Hence the four topologies of these amplifiers are as follows:. In this type of amplifier, the feedback in the circuit is designed in such a way that the output signal applied to input is in series connection.
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