This article discusses different types of feedback amplifiers - series-shunt, shunt-series, series-series, shunt-shunt and their effect on amplifier performance. It also provides a performance analysis of feedback on gain. The article includes numerical problems and circuit diagrams for better understanding.
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AssignmentVoltage Amplifier/Series-shunt FeedbackSeries-shunt amplifiers are designed to amplify a source voltage signal and provide an outputvoltage signal. The voltage amplifier is essentially a VCVS device. The input impedance ofthis source has to be high, and the output impedance should be very low.Since at the input side, the connection is series and at the output side, the connection isparallel, therefore, this kind of amplifier feedback topology is called as series- shuntfeedback.Current Amplifier/Shunt-Series FeedbackHere, the output physical quantity is current; therefore the feedback network should be ableto sample the current. The feedback signal should be in the form of so that it can get mixed inparallel with the input source current. Therefore the amplifier feedback topology which suitsour requirement is the current-mixing current-sampling topology. Since the connection at theinput is shunt and the connection at the output is series, therefore the feedback topology isalso known as shunt-series feedback. This topology stabilizes the current gain and alsoprovides a low input resistance and a high output resistance. These are two desirableproperties for a current amplifier.
Transconductance Amplifier/Series-Series FeedbackThis amplifier is known as trans-conductance amplifier since the gain of the amplifier givesthe ratio of current to voltage. In this amplifier, voltage is the input signal and current is theoutput signal. Since the series connection exists at both the input and the output side, thefeedback topology is also known as series-series feedback.Transresistance Amplifier/Shunt-Shunt FeedbackIn trans-resistance amplifiers the input signal is current and the output signal is voltage. Itfollows that the appropriate feedback topology is of the current-mixing voltage-samplingtype. The presence of the parallel (or shunt) connection at both the input and the outputmakes this feedback topology also known as shunt-shunt feedback.
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