Ideal diode as a demodulating device

[Lord Loh.]

I was just wondering, if the diode were ideal, could it be used as a demodulating device?

By ideal diode I mean that the diode would behave as a conductor in forward bias stage.

What do you think ?

 

[freewilly30]

Re: Ideal Diode.

sure it works
it is used in switching demodulators with half cycle 50%
as if u multiply the signal by a pulse train

 

[flatulent]

Re: Ideal Diode.

You will get a series of half waves of the RF whose amplitude is proportional to the amplitude modulation at that instant in time. These half waves will have a DC component that is changing with the modulation.

It was quite common in the past to use such ideal diodes in communication theory books to describe envelope demodulation.

 

[Lord Loh.]

Re: Ideal Diode.

I still do not figure out how it could demodulate ?

I belive that the ideal diode characteristics is as:
**broken link removed**

X asis is the Voltage and Y axis the current.

 

[samcheetah]

Re: Ideal Diode.

in an envelope detector an AM signal is converted into voice. the diode acts as a rectifier where it turns on when the signal is positive and turns off when the signal is negative. the capacitor after the diode charges upto signal voltage whenever the diode is forward biased i.e. the signal is positive. and it discharges when the diode is in the non-conducting state i.e. the signal is negative. now if the RC time constant is wisely chosen then the voltage across the capacitor will be the audio (or information) signal.

in the case of an ideal diode the situation will be better. an ideal diode is a closed switch in the forward biased condition. while a real world diode needs a certain voltage to turn it on. so if you replace the real world diode with an ideal diode in an envelope detector then the output will follow the input AM more better.

i hope that helps