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Feedback is an integral part of our lives. Try touching your fingertips with your eyes closed; you may not succeed the first time because you have broken a feedback loop that ordinarily “regulates” your motions. The regulatory role of feedback manifests itself in biological, mechanical, and electronic systems, allowing precise realization of “functions.” For example, an amplifier targeting a precise gain of 2.00 is designed much more easily with feedback than without. | Electronic Circuits Part 2 Teacher Dr. LUU THE VINH Chapter 12 Feedback Feedback Feedback is an integral part of our lives. Try touching your fingertips with your eyes closed you may not succeed the first time because you have broken a feedback loop that ordinarily regulates your motions. The regulatory role of feedback manifests itself in biological mechanical and electronic systems allowing precise realization of functions. For example an amplifier targeting a precise gain of 2.00 is designed much more easily with feedback than without. This chapter deals with the fundamentals of negative feedback and its application to electronic circuits. The outline is shown below. Feedback General Considerations F Amplifiers and Sense Return Methods o Analysis of Feedback Circuits stability and Compensation Loop Instability Phase Margin Frequency Compensation Elements of Feedback Systems Loop Gain Properties of Negative Feedback Types of Amplifiers Amplifier Models Sense Return Methods Polarity of Feedback Four Types of Feedback Effect of Finite I O Impedances 12.1 General Considerations As soon as he reaches the age of 18 John eagerly obtains his driver s license buys a used car and begins to drive. Upon his parents stern advice John continues to observe the speed limit while noting that every other car on the highway drives faster. He then reasons that the speed limit is more of a recommendation and exceeding it by a small amount would not be harmful. Over the ensuing months John gradually raises his speed so as to catch up with the rest of the drivers on the road only to see flashing lights in his rear view mirror one day. He pulls over to the shoulder of the road listens to the sermon given by the police officer receives a speeding ticket and dreading his parents reaction drives home now strictly adhering to the speed limit. John s story exemplifies the regulatory or corrective role of negative feedback. Without the police officer s involvement John would probably .