While if 1 + GH is smaller than 1 then the sensitivity is higher. Thus, if 1 + GH is greater than 1 then the sensitivity is lower. This is so because the sensitivity of the closed-loop system is the inverse of 1 + GH. The sensitivity offered by a positive feedback system is lesser than a negative feedback system.A positive feedback system is less stable in comparison to a negative feedback system.While the phase shift in case of the negative feedback circuit is 180°. The phase shift offered by the positive feedback circuit is either 0° or 360°.On the contrary, the overall gain with the system possessing negative feedback is less than the gain of the system with no feedback. The overall gain of the system that incorporates positive feedback is more than the gain of the system in the absence of feedback.In the op-amp circuits, the non-inverting input terminal is used to provide positive feedback to it, whereas, the inverting input terminal is used in the same to provide negative feedback.While in negative feedback, the input and output signals are of different phases thus the two are subtracted. In positive feedback, the input and output signals are of similar phase and so the two signals get added.As against, when a system uses negative feedback then it decreases the overall input of the system by subtracting the feedback signal from the actually applied input. When positive feedback is employed in a system then it increases the effective input of the system by adding the actual input with the feedback signal.Key Differences Between Positive and Negative Feedback The negative feedback system is mostly useful in amplifier circuits. The gain of the system with negative feedback is low in this case. Here the input and output signals are out of phase so the two signals get subtracted and their difference is achieved. The figure here shows the negative feedback configuration of op-amp: This signal is referred as an error signal and used to correct the variation in achieved output from the desired one in the control system. Thus, the two signals at the input of the system get subtracted and the difference of these two signals further drives the system. ![]() Here the signal at the output which is out of phase with respect to the input is fed back to the input. Negative feedback also referred as degenerative feedback is a widely used type of feedback in the control system. The positive feedback systems are majorly employed in oscillator circuits. The gain of the system when employed is a control system is high. ![]() The figure below op-amp configuration with positive feedback: This facilitates adding the feedback signal with the reference input and the added signal further acts as the controlling signal for the system in which the feedback loop is incorporated. Positive feedback or regenerative feedback is the one that takes the output signal which is in phase with the applied input and fed it back to the reference input. Transfer function of system with respective feedback Sum of applied input and fed back signal.ĭifference of applied input and fed back signal ![]() Smaller than the gain of the system where feedback is absent. Greater than the gain of the system where feedback is not present. Now, let us explore the various differentiating factors between the two. This facilitates the generation of an error signal which is used by the controller to adjust the necessary input to get the desired output.įeedback plays a crucial role in control systems thus find various applications in the process control system, amplifier, and oscillators, etc. However, both positive and negative feedback possess unidirectional behaviour in the signal flow.įeedback is considered to be a major part of a closed-loop control system that utilizes negative feedback in order to provide a sampled output signal back to the input. The signal can be either current or voltage depending on the operation. ![]() In positive and negative feedback, the relationship between input and output is in-phase and out-phase respectively.įeedback in the control system is defined as a way of providing output (or a part of the output) back to the input.
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