For an experiment, I need to build a little Lock-In Amplifier an my own circuit. I do not have an external Lock-In and so this will be the cheaper and better solution.
The circuit is nearly finished. What lacks is a circuit which should be controlled by an external oscillator and produces a two output signals, a TTL signal of the same frequency and another of 90 degrees phase shifted. The frequency range should be about 10 Hz to 10 KHz (7 decades).
I thought about first producing a sine and a cosine signal which I am going to convert to TTL afterwards.
In "The Art of Electronics" p 294, if found an interestin circuit using the AD639. Unfortunately, our official provider Farnell doesn't offer the IC saying it wouldn't be produced nomore.
There is another circuit on the next page using a lot of resitors and capacities, but it only works for 2 decades instead of seven and honestly, I would not even know how to calculate the necessary values ;)
Finally, having tried another couple of ideas, I still don't figure out how I can solve my problem. This is why I post on this forum. How could I compose a circuit dephasing either two sinusoidal or digital signals by 90 degrees (and if possible, without too much costful and placetaking electronic circuitry)?
I hope someone could help me.