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Electronics/ac analysis of the amplifier


while calculating the bandwidth from the frequency response of the amplifier,why do we take 3dB bandwidth.?what is the need to take 3dB.?

3db is merely a convenient point for referencing. It could be any other point that is agreed upon by users of such data.  However, this chosen point is the half-power point and is easy to calculate when using most simple ac circuit analysis.  Also, the db scale on voltmeters and other instrumentation are calibrated such that 3db is an easy reading point.

In filter design it is necessary to have points of reference in order to characterize the nature of its frequency performance.  Having such reference points as -3db, -6db, -12db per octave and such helps one to know the merits of the filter qualities.

What point would you use that is better?  Do you have a suggestion?

Hope this helps.  


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Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

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