Power Supplies (work in progress)

Power Supplies: Power for your projects

  • Batteries
    • What’s the difference between 9V, AAA, AA, C, and D
    • Battery chemistry
      • Carbon/zinc, lead/acid, Ni/Cd, Ni/Mh, Lithium/?
  • Converting a line voltage to a lower voltage
    • Linear
      • Unregulated
        • Voltage drop on internal resistance
      • Regulated
    • Switching
    • How much current will they deliver?
      • Depends on how much your circuit wants, and NOT on the power supply (I=V/R)
      • But, power supplies have limits to how much current they can deliver:
        • Linear: transformer magnetic saturation
        • Overheating
        • Switching power supplies often, but not always, have a circuit which shuts down the supply if the load demands too much current
    • How can you tell the two apart?
      • Weight
      • Appearance

Make a lower voltage from a higher voltage with voltage regulators

  • 7805
  • LDO regulator
  • What does it do with the excess voltage?
    • P = V * I
  • Works on any power supply (including batteries) so handy for regulating an unregulated supply (but be aware of the drop out voltage)

Op amp

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