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Desired Sinewave Generator IC

I understand. The feedback loop of the Sigma-Delta-Sigma takes care of a-priori unknown waveforms and any variations in the following filter and load (assuming you sample after the filter). For a fixed sinewave and RC filter the output pulse sequence could be determined beforehand and no feedback loop required as long as the DC offset was set by one or more resistors. All other things being equal this should allow for a faster output rate.

The audio Delta-Sigma usually has a high order low-pass filter to remove ripple and some will pass through an RC filter. Since even with a six pin uC solution there will be 4 port pins available, it makes sense to consider a higher order approach using three (+/0/-) or more output levels (4 pins allow for 7minus/0/7plus levels), using one current setting resistor per pin, that will reduce filtering requirements and ripple. The output current sequence is set beforehand based upon the desired RC output error, and slope error, and the resistors do not even have to be in exactly a 1/2/4/8 ratio as any close ratio can be taken into account when establishing the output data.

DH

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Reply to
DH1
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LOL! You obviusly don't understand what the OP is after, and what this thread is about. A function gen would be rather hard to solder onto a PCB, and would take up considerable PCB realestate :->

Dave.

Reply to
David L. Jones

Not so much 'consider', as encourage someone to whine that there's no demand, and allow managers to be scared off.

If it were REALLY an issue of 'no demand', the first such oscillator-in-a-chip would be gathering dust on the shelf. There's no such oscillator, because it IS a difficult task to make a true, pure sinewave with a mass-producible hardware base. The old HP 200 audio generator got its second feedback loop (the amplitude control) from an incandescent lamp (a component akin to 'ballast tubes'). Newer designs use the voltage-controlled-resistance region of a selected-part jFET. In each case, it isn't "standard" engineering practice, but a clever trick that saves the design.

Making a tunable oscillator of the Wein bridge type requires twin variable resistors (or capacitors); this is not easy to do on a chip (unless you have very low expectations of tuning range). It would be VERY useful (and would obviate a lot of DDS hardware) to have a high purity sinewave wide range VCO that could be locked to a squarewave clock.

Digital sinewaves are expensive, analog triangle/sine conversion is imprecise. Single-frequency high purity generators are incompatible with logic control systems.

Let's disregard the economics of a design that doesn't exist: the XR2206 DOES sell, and at a relatively high price for a single chip. A better chip would probably sell, too, and we won't know anything about the cost until we, designers, design one.

Reply to
whit3rd

Another trick:

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Even Bob Noyce tried to patent it back in 1961 or 1962, I think.

Jon

Reply to
Jon Kirwan

Hmm, looking at the I-V curve given here, this guy is putting 2000 to 10000 mA through a 2N2222A to get his negative resistance. He must know something I don't know... I'm sure that would give my 2N2222A a negative *existence* !!!

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

Reply to
Bob Masta

No. I thought that, but then I saw the table of voltage vs. current. The voltages also have commas in them, like this "6,35".

A fact for you: Many non-British European countries use a comma where Britain and America use a dot, for a decimal point. So they would write pi as "3,14159..." rather than "3.14159...".

The website is French (.fr):

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Martin

Reply to
Fleetie

Um, did you look at his schematic? There is a 1k resistor with a 12V supply and the statement of I=6mA. They use commas for radix points, in much of Europe.

Yes, all the Europeans who do that should just cave in and come on over to the USA way of doing things which obviously makes a whole lot more sense. ;) But then, sometimes I just accept the fact that I can't change people and go with the flow.

Jon

Reply to
Jon Kirwan

Hey guys... I was *joking*! (Or trying to...) It was supposed to be a play on "negative resistance" versus "negative existence", see... Oh, never mind! I'll try to stay away from the catnip...

(Yes, I saw the schematic... and I do know about Euro-commas-as-decimals.)

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

Reply to
Bob Masta

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