In feedback process explain how input impedance and output impedance varies with respect to input and output voltage and current at each type of feedback circuit.
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Answer:
Feedback Systems
In a Feedback System, all or part of the output signal either positive or negative is fed back to the input
Feedback Systems process signals and as such are signal processors. The processing part of a feedback system may be electrical or electronic, ranging from a very simple to a highly complex circuits.
Simple analogue feedback control circuits can be constructed using individual or discrete components, such as transistors, resistors and capacitors, etc, or by using microprocessor-based and integrated circuits (IC’s) to form more complex digital feedback systems.
As we have seen, open-loop systems are just that, open ended, and no attempt is made to compensate for changes in circuit conditions or changes in load conditions due to variations in circuit parameters, such as gain and stability, temperature, supply voltage variations and/or external disturbances. But the effects of these “open-loop” variations can be eliminated or at least considerably reduced by the introduction of Feedback.
A feedback system is one in which the output signal is sampled and then fed back to the input to form an error signal that drives the system. In the previous tutorial about Closed-loop Systems, we saw that in general, feedback is comprised of a sub-circuit that allows a fraction of the output signal from a system to modify the effective input signal in such a way as to produce a response that can differ substantially from the response produced in the absence of such feedback.
Feedback Systems are very useful and widely used in amplifier circuits, oscillators, process control systems as well as other types of electronic systems. But for feedback to be an effective tool it must be controlled as an uncontrolled system will either oscillate or fail to function. The basic model of a feedback system is given as:
Feedback System Block Diagram Model
feedback systems block diagram
This basic feedback loop of sensing, controlling and actuation is the main concept behind a feedback control system and there are several good reasons why feedback is applied and used in electronic circuits:
Circuit characteristics such as the systems gain and response can be precisely controlled.
Circuit characteristics can be made independent of operating conditions such as supply voltages or temperature variations.
Signal distortion due to the non-linear nature of the components used can be greatly reduced.
The Frequency Response, Gain and Bandwidth of a circuit or system can be easily controlled to within tight limits.
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