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

[Magnus Danielson]

Hej,

On 08/14/2014 02:16 PM, Ove Ridé 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.)

I would consider building a Gilbert cell out of transistors. MC1495/1496 
is an example, but you can build it out of discrete transistors.

Cheers,
Magnus