[sdiy] On the topic of ring modulation (Using FETs instead of diodes?)

[Tom Wiltshire]

Perhaps you could try using four precision rectifier circuits in the ring configuration to overcome the diode turn-on threshold. Diode ring modulators usually use germanium diodes for the lower threshold voltage, but with the precision rectifier circuit, you could probably use cheap silicon diodes - 1N4148s or whatever.

Just a thought - I haven't tried it.

Tom

On 14 Aug 2014, at 13:16, Ove Ridé <nitro2k01 at gmail.com> wrote:

> I just watched this video and got reminded of the diode ring mixer
> topology of ring modulators.
> 
> https://www.youtube.com/watch?v=junuEwmQVQ8
> 
> As mentioned in the video, the diode ring mixer has the issue that
> there are dead spots when the carrier is near zero, because of the
> diode turn on threshold. This got me thinking, what if you instead
> used FETs, perhaps driven by a comparator, instead of diodes? This
> should, if done well, get rid of that non-linearity, as far as I can
> tell.
> 
> And to ask a slightly different question, how would one design a high
> quality analog ring modulator for audio frequencies, using modern,
> jelly bean parts? (That is, non-specialized parts, as well parts that
> didn't go out of production 10-20 years ago.)
> 
> -- 
> /Ove
> 
> Blog: <http://blog.gg8.se/>
> 
> "Here is Evergreen City. Evergreen is the color of green forever."
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