XOR MIXER to extract difference component using a dirty RC low pass filter

230

04:42:29

This is for @Hurz

It is a dirty way to achieve extraction of only the difference (the Difference being 300 Hz and the Sum being 1.7 KHz) using an XOR gate as a mixer without employing LC filtering.

Here I have used 5 volt logic which may just work using the 74HC series logic gates. I have NOT tested this, but I will if I find the time.

I have set this circuit to use 5 volt logic.
Therefor I have biased the signal generators with a 2.5 volt DC offset.
The AC component of the generators is set at 50 mV

At the output of the gate, there is a really grotty and nasty filter set to start at about 150 Hz. In practice this cut-off point is usable but you could experiment...... or tell me how wrong I am etc...

I admit that this whole scheme is quite horrible and is obviously quite useless for RF. However, it may prove to be interesting for audio effects which is why I am interested in this technique.

(As usual, I now completely openly welcome ALL mindless AND/OR mindful comments even if they do come from highly expert Electronics Engineers who have NEVER used and maybe never seen a soldering iron --- Bring it on!!!)

N.B. As this is not anywhere near normal RF frequencies, a solder-less breadboard may be OK to build this circuit. Having said this, I will warn that most of the cheaper solder-less breadboards have no ground plane under the contacts and this often causes horrible nasty hum problems. You will also find stray capacitance and inductance affects your results with this prototyping technique.

Enjoy

73

published 9 years ago

hurz

9 years ago

Yes why not a RC filter. I demonstrated both mixer products difference and sum frequency. LC filter are more efficient so the diff freq for example i get about 280mVpp and this is only cuz i limited the corner freq to keep the voltages comparable. The gates output lowpass damped the sum mixer products. But all in all both circuits are identical.

hurz

9 years ago

This is what you reference, right? http://everycircuit.com/circuit/5752938423648256

zorgrian

9 years ago

Yes, that's the inspiration for this circuit.

zorgrian

9 years ago

I stayed up way too late last night trying to get this working with a gate from a 74HC86. I don't have a dual signal generator and this is on my list of projects to build. However I built a 1 KHz oscillator and used the signal generator to provide me with the 700 Hz. The result was far from perfect but it does work!

hurz

9 years ago

And sure you can do that with RC 2. Order low pass. I just like it with LC cuz of smaller topology here in simulator. In reality i would also use RC for simplicity ;-)

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