Frequency Mixer Op Amp

This is a summing OP-amp. To me, “Frequency Mixer” means “analog multiplier”, because in RF (radio frequency) terms, mixer means analog multiplier and is used for all kinds of strange effects involving adding and subtracting frequencies.

No, not much difference?

I've got a question... Why do you have the capacitors and have a 10k resistor from the non-inverting terminal to ground? Won't it function just fine without?

Yes, but the capacitor is to remove any bias the OP-amp has and the 10kOhm resistor, well, I’m not sure but there is probably a similar reason involving imperfection of the OP-amp.

@sshsslfun, not much difference between what you’ve posted here and analog multiplier? What you have is an analog adder. Addition is not multiplication. They produce completely different results, especially when analog and with sine waves. If you multiply a 1kHz signal by a 900Hz signal, you get a 100Hz (1kHz-900Hz) signal added with a 1.9kHz (1kHz+900Hz) signal. With an adder, you get a 1kHz signal added with a 900Hz signal. Completely different. A multiplier will produce what looks like a sine wave (at 1.9kHz) whose center varies across the scope in a sine wave pattern (at 100Hz). With an adder, you will get what looks like a suppressed carrier AM signal (which looks similar to regular AM).

Gotcha, thanks

Would you mind providing an example of an analog multiplier? It sounds interesting to me. :) I think I know what an analog adder is

Here is Jason's multiplier: http://everycircuit.com/circuit/5523779525804032

I think Hurz used one of the logic gates as a analog multi but they changed how gates function. As you can see from Jason's multiplier, there isn't much room left over. We really need a solution from the developer.

DAC needs external reference input. page 807

Thanks man!

Here an example of what @rich11292000 mentioned http://everycircuit.com/circuit/5626258821218304

Yes the xnor. I remembered but didn't learn. Thank you.

XOR, XNOR, doesn't matter which one

What purpose does the cap serve in this circuit?