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Unformatted text preview: ECEN 326 Electronic Circuits Feedback Dr. Aydın ˙ Ilker Kar¸ sılayan Texas A&M University Department of Electrical and Computer Engineering Ideal Feedback Configuration Ideal Feedback Configuration ε S fb S o S i S Feedback Network Basic Amplifier a f Σ S o S i = A = a 1 + T , T = af S ε S i = 1 1 + T , S fb S i = T 1 + T ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 1 Effect of Feedback Effect of Feedback Gain sensitivity Gain of the basic amplifier ( a ) usually depends on temperature, operating conditions and process parameters. dA da = (1 + af)- af (1 + af) 2 = 1 (1 + af) 2 δ A = δ a (1 + af) 2 ⇒ δ A A = 1 + af a δ a (1 + af) 2 δ A A = δ a a 1 + af = δ a a 1 + T ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 2 Effect of Feedback Effect of Feedback Distortion S o S ε a 3 a 1 a 3 a 2 a 2 S o1 a 1 S o2 S o1 S o S i A 3 A 1 A 2 A 2 A 3 S o1 a 1 (1+a 1 f) S o2 S o1 A 1 = a 1 1 + a 1 f ≈ 1 f , A 2 = a 2 1 + a 2 f ≈ 1 f ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 3 Two-Port Networks Two-Port Networks y parameters i 2 2 v y 21 v 1 y 22 i 1 v 1 y 12 v 2 y 11 1 Two-port network 1 i 1 = y 11 v 1 + y 12 v 2 i 2 = y 21 v 1 + y 22 v 2 y 11 = i 1 v 1 v 2 =0 , y 12 = i 1 v 2 v 1 =0 y 21 = i 2 v 1 v 2 =0 , y 22 = i 2 v 2 v 1 =0 ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 4 Two-Port Networks Two-Port Networks z parameters i 2 i 1 Two-port network 2 v 1 v 2 12 z i z z 21 i 1 z 11 22 v 1 = z 11 i 1 + z 12 i 2 v 2 = z 21 i 1 + z 22 i 2 z 11 = v 1 i 1 i 2 =0 , z 12 = v 1 i 2 i 1 =0 z 21 = v 2 i 1 i 2 =0 , z 22 = v 2 i 2 i 1 =0 ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 5 Two-Port Networks Two-Port Networks h parameters i 1 1 v h 11 v 2 h i 2 22 2 h 21 i 1 h 12 v 1 Two-port network v 1 = h 11 i 1 + h 12 v 2 i 2 = h 21 i 1 + h 22 v 2 h 11 = v 1 i 1 v 2 =0 , h 12 = v 1 v 2 i 1 =0 h 21 = i 2 i 1 v 2 =0 , h 22 = i 2 v 2 i 1 =0 ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 6 Two-Port Networks Two-Port Networks g parameters i 1 v 1 1 i 2 g v 2 21 g 22 i 2 g 12 v 1 g 11 Two-port network i 1 = g 11 v 1 + g 12 i 2 v 2 = g 21 v 1 + g 22 i 2 g 11 = i 1 v 1 i 2 =0 , g 12 = i 1 i 2 v 1 =0 g 21 = v 2 v 1 i 2 =0 , g 22 = v 2 i 2 v 1 =0 ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 7 Feedback Configurations Feedback Configurations According to whether the output signal S o is a current or a voltage and whether the feedback signal S fb is a current or a voltage, four feedback configurations exist: Series-Shunt Feedback S fb = v fb (voltage), S o = v o (voltage) Shunt-Shunt Feedback S fb = i fb (current), S o = v o (voltage) Shunt-Series Feedback S fb = i fb (current), S o = i o (current) Series-Series Feedback S fb = v fb (voltage), S o = i o (current) ECEN 326 Electronic Circuits - Aydın ˙ I. Kar¸ sılayan - Feedback 8 Series-Shunt Series-Shunt Ideal v ε z o v o av i z ε o v i i fv i Basic amplifier...
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This note was uploaded on 02/08/2009 for the course ECEN 326 taught by Professor Karsilayan during the Spring '09 term at Texas A&M.

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feedback - ECEN 326 Electronic Circuits Feedback Dr. Aydın...

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