Freq mixer

In principle, yes. You can prove its correct functioning by adding a 300Hz low pass and/or 1700Hz high pass filter.

I added a low pass filter fc=400 Hz and nothing change

Yes, and even if u use an opamp first to not load your mixer and use a better filter it doesn't show a lot modulation.

If you watch the op amp output whilst reducing the 1k source to 700 ohm you will see that the wave form settles nicely at 700. Likewise alter just the 700 source to become 1k and the output settles at 1k. That is a good indication of the frequencies being mixed here. If you wish to use a filter then a notch filter might be better than a high or low pass since it would take out a more specific chosen frequency, thus leaving just the other frequency visible. Another option would be to perform a Fourier transform on your output wave....that would show you the individual makeup frequencies there.

2ctiby do you have any example using fourier transform in a circuit?

I supose that I need a active filter.. amp. Op. + filter I Don't think it's the best way to get the 1700 Hz signal. Output signal is too destroyed

There are various software packages which do fourier transforms. Possibly spice? etc. Perhaps the best bet is to download a free audio package such as Audacity. You would then need to build the circuit and record its output in to the package.....easy going from there....you can even obtain the output as raw data to mess with if you wish. I use a free package from many years back called Soundforge5 (may be worth looking for it...but it got taken over some years ago and it costs now). The Sonogram feature does a great adjustable colourful transform in that package, but Audacity is better in other features and it's free.

700Hz mixed together with 1kHz suppose to give 300 and 1700 plus an offset DC.

http://everycircuit.com/circuit/5752938423648256

Gracias thanks you

You are welcome! Mucho gusto!

Anyway, beside this multiplier hack for EC you can use XOR gates in reality as mixer/multiplier. See this example http://everycircuit.com/circuit/6159394264317952

Anyways this circuit do adding not multiplier !!it's wrong!

Which circuit?

My circuit "freq mixer" tomorrow will try to fix it

right. Keep it up!

Extremely messy circuit. It would help you if you make it a bit nicer. There is enough space for a gilbert cell.