Explanation Given Information: A feedback amplifier having open-loop gain function with parameters A i o = 10 5 A/A , f 1 = 10 4 Hz , f 2 = 10 5 Hz and phase margin is 60 ° Calculation:: An open-loop amplifier current transfer function can be represented using its low-frequency gain and the poles as, A i = A i o ( 1 + j f f 1 ) ( 1 + j f f 2 ) Here, based on the low frequency gain and the poles given, the open loop current transfer function becomes, A i = 10 5 ( 1 + j f 10 4 ) ( 1 + j f 10 5 ) Therefore, the loop gain is given by, T ( f ) = A ( f ) β The frequency corresponding to the given phase margin is to be calculated so that it can be used to find the feedback factor as follows. The phase margin represents the phase angle ϕ , such that the magnitude of loop gain is unity at a frequency corresponding to a phase of 180 ° − ϕ . For the given phase margin ϕ = 60 ° , the phase for the given function is, 180 ° − 60 ° = 120 ° . This gives the phase of the given loop gain, − ( 180 ° − 60 ° ) = − tan − 1 ( f 10 4 ) − tan − 1 ( f 10 5 ) − 120 ° = − tan − 1 ( f 10 4 ) − tan − 1 ( f 10 5 ) Now, using the trigonometric identity, tan − 1 ( A ) − tan − 1 ( B ) = tan − 1 ( A + B 1 − A B ) , the expression on the right hand side of the above equation can be rewritten as follows. tan − 1 ( f 10 4 ) + tan − 1 ( f 10 5 ) = tan − 1 ( f 10 4 + f 10 5 1 − f 10 4 × f 10 5 ) = tan − 1 ( 11 f × 10 4 10 9 − f 2 ) Taking tangent of angle on both sides, tan ( 120 0 ) = tan ( tan − 1 ( 11 f × 10 4 10 9 − f 2 ) ) − 1

Microelectronics: Circuit Analysis and Design

4th Edition

ISBN: 9780073380643

Author: Donald A. Neamen

Publisher: McGraw-Hill Companies, The

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Chapter 12, Problem 12.16TYU

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The value of feedback factor for the given values.

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Chapter 12, Problem 12.15TYU

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Chapter 12 Solutions

Microelectronics: Circuit Analysis and Design

Ch. 12 - (a) The open-loop gain of an amplifier is A=5104...Ch. 12 - (a) Consider a general feedback system with...Ch. 12 - (a) A feedback amplifier has an open-loop...Ch. 12 - (a) Consider the circuit shown in Figure...Ch. 12 - (a) The closed-loop gain of a feedback amplifier...Ch. 12 - The gain factors in a feedback system are A=5105...Ch. 12 - Prob. 12.3TYU Ch. 12 - An ideal series-shunt feedback amplifier is shown...Ch. 12 - Consider the ideal shunt-series feedback amplifier...Ch. 12 - An ideal series-series feedback amplifier is shown...

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The value of feedback factor for the given values.

Solution Summary: The author describes an open-loop amplifier with low-frequency gain and the poles. The frequency corresponding to the given phase margin is to be calculated to find the feedback factor.

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The value of feedback factor for the given values.

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Chapter 12 Solutions