I'm trying to understand the workings of a full wave bridge rectifier and would like some help. The output I got is shown below, and I'm wondering with a 6.3V rms input, why is the output amplitude so much less than this? Is there a way to calculate this amplitude?

Additionally, why are there flat spaces between each of the waves? Where do these flat spaces come from?

Thanks! enter image description here

  • \$\begingroup\$ Please add a circuit diagram, and show the points where you are making the measurement. (hit Ctrl-M to open the schematic editor) \$\endgroup\$ – Peter Bennett Apr 25 '17 at 0:57
  • 2
    \$\begingroup\$ Are you sure that's 6.3V rms? What you have there is closer to what I'd expect to see if you had 6.3V peak. \$\endgroup\$ – Hearth Apr 25 '17 at 0:59
  • \$\begingroup\$ Flat spaces are when voltage gets below 0.7V and -0.7V, respectively. \$\endgroup\$ – StainlessSteelRat Apr 25 '17 at 1:51
  • \$\begingroup\$ needs capacitors to get the most out... \$\endgroup\$ – dandavis Apr 25 '17 at 4:28

Both of your questions are answered by this simple fact: When a diode is conducting, it will have a voltage drop across it. For your standard silicon diode (1N4148, 1N4001, etc), this is somewhere around 0.5~0.7V under normal conditions (it increases slightly at high currents). For Schottky diodes, it's closer to 0.2~0.3V, germanium diodes are around 0.3~0.4V, and very high power diodes can be very high, up to multiple volts or even tens of volts.

Since in a bridge rectifier, two diodes are conducting at any one time, you'll be losing two diode drops worth of voltage; this explains your reduced voltage. The flat bits are a consequence of this as well: if there isn't enough voltage to turn the diodes on, they simply won't conduct.


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