Desired Sinewave Generator IC

[DH1]

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



On Mar 10, 3:31 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Tue, 10 Mar 2009 02:19:49 -0700 (PDT), DH1 <newste...@iol.ie
wrote
clipped

For delta-sigma, a periodically-run software loop, every pass through,
sets a port pin either high or low. The average (rc lowpass filtered)
voltage of that pin makes the desired sinewave, with of course a Vcc/2
DC offset. D-S differs from PWM in that the pulse train is
statistical, not rigidly deterministic, and there's no duty-cycle
quantization as with PWM. This is the "one-bit DAC" that some CD
players use.

I don't know how high a frequency a PIC could make... it depends on
compute power.

John

 

[David L. Jones]

<jamesgangnc@gmail.com> wrote in message
news:94859ad4-101c-4a32-aa98-1a3bf35d4666@v38g2000yqb.googlegroups.com...
On Mar 10, 7:22 am, "David L. Jones" <altz...@gmail.com> wrote:

"DH1" <newste...@iol.ie> wrote in message

news:d46d1a08-e905-4f69-96bd-be9797ad21d1@w9g2000yqa.googlegroups.com...
Well yes. I did not state that demand was high only that I desired it
and it would be useful for many applications. A low cost SOT23-5
design would minimize board space and passive requirements.
Applications include IR/Ultrasonic sensing/communication carrier
waves, high freq. power circuits, sine tone generation, etc. and the
list is likely almost as long as the number of contributors. I also
see other posts looking for a similar part, and there are many circuit
designs available attempting with different degrees of success to
provide minimal &/or low distortion sinewave generators.

If I need a single sinewave I will select a lower cost resistor
configured SPT23-5 part over an XR2206 everytime. The same would apply
for multiple sinewaves, or freq. &/or amplitude modulation designs.

Whether or not the part is currently economically viable I cannot be
certain, however based upon its merits I suspect that at the right
price it is. In the past I have found myself looking for something
that did not exist, yet did appear on the market a short time later
(SSDs are one example) and this can be a case of many people
recognizing a need and the required technological state of development
at the same time.

The prior development path that you outline is very interesting (and
I agree that the requirements for triangle/square & sine wave
generation are substantially different), however remarkable new
designs keep appearing on the market, such as programmable micro
crystal oscillators, digital pots, or a low cost 0.4uV offset 5MHz R2R
1.1mApower opamp in an SOIC8 format, as manufacturers push back the
boundaries. It may well soon be time to rethink the sinewave generator
and develope a med-high spec almost trivial to configure option(s) in
a minimal package, perhaps using PLL, MEMs, state machine/uC internal
control/stabilization, uPower techniques etc.

It gets my vote. I seem to be always in need of just such a simple sine
wave
generator, the last time being last week when all I wanted was a 1kHz 1V
sine wave as a test signal on a board. A few % distortion would have been
fine.
It's always amazed me that a simple SOT-23-5 or SO8 device like that has
not
been produced.
If you build it, they will come...

Dave.- Hide quoted text -

- Show quoted text -

Buy a used function generator off ebay and be done with it.

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.

 

[Jon Kirwan]

On Sat, 14 Mar 2009 12:39:42 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

If it was simple to generate a good sinewave, then there'd have
been such a device long ago.  But it's not, so they have to consider
how much demand for it.

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.
snip

Another trick:
http://jlnlabs.online.fr/cnr/negosc.htm

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

Jon

 

[whit3rd]

If it was simple to generate a good sinewave, then there'd have
been such a device long ago.  But it's not, so they have to consider
how much demand for it.

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.

If there's little demand, then the cost goes up.

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.

 

[Bob Masta]

On Sat, 14 Mar 2009 20:04:53 GMT, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sat, 14 Mar 2009 12:39:42 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

If it was simple to generate a good sinewave, then there'd have
been such a device long ago.  But it's not, so they have to consider
how much demand for it.

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.
snip

Another trick:
http://jlnlabs.online.fr/cnr/negosc.htm

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

 

[Fleetie]

Bob Masta wrote:

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

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): http://jlnlabs.online.fr/cnr/negosc.htm


Martin

 

[Jon Kirwan]

On Sun, 15 Mar 2009 13:49:31 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sat, 14 Mar 2009 20:04:53 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 14 Mar 2009 12:39:42 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

If it was simple to generate a good sinewave, then there'd have
been such a device long ago.  But it's not, so they have to consider
how much demand for it.

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.
snip

Another trick:
http://jlnlabs.online.fr/cnr/negosc.htm

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* !!!

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

 

[Bob Masta]

On Sun, 15 Mar 2009 18:37:03 GMT, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sun, 15 Mar 2009 13:49:31 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sat, 14 Mar 2009 20:04:53 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 14 Mar 2009 12:39:42 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

If it was simple to generate a good sinewave, then there'd have
been such a device long ago.  But it's not, so they have to consider
how much demand for it.

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.
snip

Another trick:
http://jlnlabs.online.fr/cnr/negosc.htm

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* !!!

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

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...
<g>

(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
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!