diode's effect on voltage

[Peter M]

Question from a greenhorn: what effect will using a single diode to rectify an AC voltage have on the output voltage? Will it decrease, or stay the same? (i.e., will an AC input of 16V become a DC output of 16V?
And, if it is not the voltage that changes, what does?

 

[audioguru]

When you rectify AC, you get a DC voltage that is higher than the AC voltage because the filter capacitor charges to the peak of the AC sine-wave which is 1.414 times hugher, minus the voltage across the rectifier diode.
With a single diode you will have twice the ripple voltage than if you used a full-wave rectifier because the capacitor discharges twice as long a time into the load.

 

[Peter M]

diode's effect....

Thanks for the reply, but need a clarification: if I want to create a DC output of 16V from an AC source using a single diode, do I begin with
8V AC?

 

[Russlk]

(16V + 0.5V)/1.414 = 11.67VAC

 

[evandude]

Thanks for the reply, but need a clarification: if I want to create a DC output of 16V from an AC source using a single diode, do I begin with
8V AC?

uh, no...

DC output = (AC voltage * 1.414) - diode voltage drop

so you just shuffle it around to get the required AC voltage, just as Russlk demonstrated before I had a chance to finish typing this message :lol:

 

[ljcox]

DC output = (AC voltage * 1.414) - diode voltage drop

This gives the peak voltage. Also, as Audio said, there will be a ripple and its amplitude will depend upon the load resistance and the capacitance of the filter capacitor. The voltage drop across the diode is also a function of its slope resistance and the current through it.

Full wave rectification (ie. a diode bridge) would be better than a single diode)