Hey guys,

I'm reading this book on Microelectrics and on of the examples they have is if you have a peak voltage of 10V and R = 1k-ohm, this would be for an AC supply voltage and circuit with a diode in it, find the peak value of the current in the diode and the dc component of the output voltage. I understand how to get the current ( V= IR), but not how to get the DC voltage output. The book just lists the value at 3.18 V, and the current at 10mA. any help would be great. Thanks

 

Can you post up the circuit?

 

Not too sure how to do that. its a pretty simple circuit with a voltage source on the left, two wires one going up the other down. the top wire has a diode in it and after that there is the positive output terminal. the bottom wire leads to the negative output terminal. And there is a resistor in parallel to the voltage source that is after the diode but before the output voltage. there is nothing connecting the two terminals of the output voltage

 

Something like this...

 

This is a half way rectifier.

The voltage across the resistor will be the source voltage minus the voltage drop across the diode.

The DC output voltage equals:
Vdc=Vm/pi

where

Vm is the peak voltage across the resistor

 

Thanks mik3, could you extrapolate on the origins of that equation, it doesnt quite make sense to me visually. And also, would you use the same equation for a full-wave rectifier? Thanks

 

Hi frisbee4all,

Assuming vm sinwt as the voltage across the resistor,the dc output is give by the average value of vm sinwt.
the average value is given by integrating Vmsin wt within the limits 0 to pi and dividing this answer by 2 pi (time period).so you get vm/pi as mik3 said.
If we use a fullwave rectifier then the time period become pi so we get 2vm/pi