Lecture_34

# Lecture_34 - Lecture 34 Page 2 The Decibel log v O/v I log...

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Introduction to Frequency Response An op-amp’s open-loop gain (the gain without feedback applied) is called A OL The device gain at DC ( f = 0 Hz) is called A o Due to internal capacitances, the open-loop gain decreases at higher frequencies If the device can be modeled as having a single, dominant pole, then the frequency response is very predictable The dominant pole frequency is called f PD The device gain is large from DC to f = f PD Above f = f PD , device gain decreases as 1/ f The unity-gain frequency is called f T + - v I 1 v I 2 v O A OL log f OL A f PD f T f f T 1 A 0 ) ( f A OL EE 310 Lecture 34 Lecture 34 Page 1

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Why Does Gain Decrease as Frequency Increases? v O + - v I + - R C v O /v I f 1.0 0.8 0.6 0.4 0.2 0 log ( v O /v I ) log f (Hz) 1 10 -1 10 -2 10 -3 10 -4 1 10 100 1 k 10 k 100 k 10 -5 EE 310 Lecture 34

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Unformatted text preview: Lecture 34 Page 2 The Decibel log ( v O /v I ) log f (Hz) 1 10-1 10-2 10-3 10-4 1 10 100 1 k 10 k 100 k 10-5 EE 310 Lecture 34 Lecture 34 Page 3 Device Frequency Response + PD OL f f j A f A 1 ) ( +-v I 1 v I 2 v O A OL log f OL A f PD f T f f T 1 A ) ( f A OL Gain at any frequency: Gain at low frequencies: Mid-frequency gain: At some frequency, the gain is unity: Device Gain-Bandwidth Product: EE 310 Lecture 34 Lecture 34 Page 4 Frequency Response Characteristics of Op Amps log f dB OL A dB CL A f PD f T f 3dB A CL (ideal) A f f T EE 310 Lecture 34 Lecture 34 Page 5...
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Lecture_34 - Lecture 34 Page 2 The Decibel log v O/v I log...

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