Berkeley ELENG 105 - Lecture 22 (26 pages)

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Lecture 22



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Lecture 22

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Lecture Notes


Pages:
26
School:
University of California, Berkeley
Course:
Eleng 105 - Microelectronic Devices and Circuits
Microelectronic Devices and Circuits Documents

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Lecture 22 ANNOUNCEMENTS Midterm 2 Th 11 15 3 30 5PM 3 30 5PM in Sibley Aud Bechtel Bldg HW 11 Clarifications revisions to Problems 1 3 4 were made OUTLINE Differential Amplifiers General considerations BJT differential pair Qualitative analysis Large signal analysis Large signal Small signal analysis Frequency response Reading Chapter 10 1 10 2 EE105 Fall 2007 Lecture 22 Slide 1 Prof Liu UC Berkeley Humming Noise in Audio Amplifier Consider the amplifier below which amplifies an audio signal from a microphone p If the power supply VCC is time varying it will result in an additional undesirable voltage signal at the output perceived i d as a humming h i noise i by b th the user EE105 Fall 2007 Lecture 22 Slide 2 Prof Liu UC Berkeley Supply Ripple Rejection Since node X and Y each see the voltage ripple their voltage difference will be free of ripple pp v X Av vin vr vY vr v X vY Av vin EE105 Fall 2007 Lecture 22 Slide 3 Prof Liu UC Berkeley Ripple Free Differential Output If the input signal is to be a voltage difference between two nodes an amplifier that senses a differential signal is needed EE105 Fall 2007 Lecture 22 Slide 4 Prof Liu UC Berkeley Common Inputs to Differential Amp The voltage signals applied to the input nodes of a differential amplifier p cannot be in phase p otherwise the differential output signal will be zero v X Av vin vr vY Av vin vr v X vY 0 EE105 Fall 2007 Lecture 22 Slide 5 Prof Liu UC Berkeley Differential Inputs to Differential Amp When the input voltage signals are 180 out of phase the resultant output p node voltages g are 180 out of p phase so that their difference is enhanced v X Av vin vr vY Av vin vr v X vY 2 Av vin EE105 Fall 2007 Lecture 22 Slide 6 Prof Liu UC Berkeley Differential Signals Differential signals share the same average DC value and are equal q in magnitude g but opposite pp in p phase A pair of differential signals can be generated among other ways by a transformer EE105 Fall 2007 Lecture 22 Slide 7 Prof Liu UC



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