4.3.3 Power Supply Filtering

Chapter 4.3.3 Power Supply Filtering

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 4. DIODE CIRCUITS71SGFigure 4.8: Full-wave rectifier and its output waveform.4.3.3Power Supply FilteringThe rectified waveforms still have a lot of ripple that has to be smoothed out in order togenerate a genuine DC voltage. This we do by tacking on a low-pass filter. The capacitorvalue is chosen in order to ensure small ripple, by making the time constant for dischargingmuch longer than the time between re-charging.4.3.4Split Power SupplyOften a circuit requires a power supply that provides negative voltage as well as positivevoltage. By reversing the direction of the diode and the capacitor (if it is polarized), thehalf-wave rectification circuit with low-pass filter provides a negative voltage.Similarly,reversing the direction of the diodes and capacitor in the full-wave rectified supply producesa negative voltage supply. A split power supply is shown in figure 4.9.GROUND-V+VSGFigure 4.9: Split power supplies.