Low frequency analog VCO with sinewave output?

On Thu, 25 Aug 2011 20:29:45 -0700, Bill Sloman wrote:

> On Aug 26, 5:26&nbsp;am, Tim Wescott <t...@seemywebsite.com> wrote:
>> On Wed, 24 Aug 2011 21:53:24 -0700,BillSlomanwrote:
>> > On Aug 25, 3:24&nbsp;am, Tim Wescott <t...@seemywebsite.com> wrote:
>> >> On Wed, 24 Aug 2011 05:15:09 -0700,BillSlomanwrote:
>> >> > On Aug 24, 7:22&nbsp;pm, davew <david.wo...@gmail.com> wrote:
>> >> >> I'm searching for a simple one chip solution if anyone has any
>> >> >> ideas. Best I've found so far might be the old 8038 function
>> >> >> generator chip.
>>
>> >> > If you are restricted to one chip, this is probably as good as it
>> >> > gets. It distorts a triangular wave to a tolerable approximation
>> >> > to a sine wave.
>>
>> >> > You can do better by feeding a square wave through a shift
>> >> > register clock at some convenient multiple of the square wave
>> >> > frequency, tying a series of resistors to the outputs of the shift
>> >> > register and summing the currents through the resistors into a
>> >> > virtual earth to produce a staircase approximation to a sine wave,
>> >> > but it takes quite a long shift register and quite a few close
>> >> > tolerance resistors to do better than the 8038, and &nbsp;it's still a
>> >> > three chip solution - basically a programmable logic device to
>> >> > provide the shift register and the dividers to generate the square
>> >> > wave, the VCO to to generate the clock at some fairly high
>> >> > multiple of the output frequency, and an op amp to sum the
>> >> > currents from the resistors, plus you have to find board space for
>> >> > the resistors.
>>
>> >> > The Analog Devices DDS chips do provide a very good one chip
>> >> > solution - the more expensive chips include 14-bit DACs - but it
>> >> > isn't an analog solution.
>>
>> >> How about a CD4040 and a bunch of resistors? &nbsp;(I think I mean the
>> >> CD4040 -- the 4020, 4040, and 4060 are all big-ass counters, one of
>> >> which has an oscillator built in).
>>
>> >> It's a ripple counter, but if you're going slow enough the clock
>> >> glitches shouldn't get you too bad.
>>
>> > Well, the CD4040 is cheap, but a progammable logic device can provide
>> > the same funcion - and a lot more beside - in a single chip, which is
>> > one of the things the OP is asking for.
>>
>> > And the CD4040 is slow - slow enough for it to be nuisance when I
>> > first used the part back in 1975. It looks glacial these days.
>>
>> At one point you could get 74HC4040 parts -- dunno if they're still out
>> there.
>>
>> I was thinking of that part because of the built-in oscillator -- what
>> programmable logic part has that?
> 
> http://www.datasheetcatalog.org/datasheet/philips/74HC4040.pdf
> 
> Some of the biggish CMOS counters RCA made at that time had built-in
> oscillator drivers, but the 4040 wasn't one of them.

Then -- as I stated in my original reply -- it's either the 4020 or the 
4060.

-- 
www.wescottdesign.com

On 8/25/2011 12:29 PM, Tim Wescott wrote:
> On Wed, 24 Aug 2011 17:57:06 -0500, Vladimir Vassilevsky wrote:
>
>> davew wrote:
>>
>>> I'm searching for a simple one chip solution if anyone has any ideas.
>>> Best I've found so far might be the old 8038 function generator chip.
>>
>> Take ATTiny13, make a predefined lookup table with pre-distorted
>> sinewave, generate a noise chaped PWM. That would be absolutely the
>> cheapest controllable and fairly accurate generator of a good quality
>> sine wave.
>
> Curiosity (well, sloth): does it have an on-board ADC?
>
> This is basically what I suggested (except I suggested a PIC).  The OP
> wants analog only, for whatever reason.

There are some Atmel microcontrollers with a built in DAC (and an 
internal oscillator) that would work. The problem is that the amplitude 
is limited to something 0.6V below the supply voltage (3.6V Max for 
Vcc), so you may need an amplifire as well. The XR2206 offers 6 V p-p 
for the sine wave.

On Wed, 24 Aug 2011 13:36:20 -0500, Tim Wescott
<tim@seemywebsite.com> wrote:

>> Interesting ideas.  From memory, doesn't the Wien-bridge oscillator need
>> some form of amplitude stabilisation?
>
>Yes, but if you don't mind a rather distorted sine wave it can be done 
>just by letting the output smack into the supply rails.  Since you 
>haven't responded to my questions about what you really need, one can 
>only assume that any old wiggly line on a scope counts as a "sine" wave.

National's AN-31 describes a "Wein Bridge Sine Wave
Oscillator" on page 8, right side, using an incandescent bulb
(Eldema 1869, with about 100k hr lifetime.)

Jon

On Fri, 26 Aug 2011 14:45:11 -0700, Jon Kirwan
<jonk@infinitefactors.org> wrote:

>On Wed, 24 Aug 2011 13:36:20 -0500, Tim Wescott
><tim@seemywebsite.com> wrote:
>
>>> Interesting ideas.  From memory, doesn't the Wien-bridge oscillator need
>>> some form of amplitude stabilisation?
>>
>>Yes, but if you don't mind a rather distorted sine wave it can be done 
>>just by letting the output smack into the supply rails.  Since you 
>>haven't responded to my questions about what you really need, one can 
>>only assume that any old wiggly line on a scope counts as a "sine" wave.
>
>National's AN-31 describes a "Wein Bridge Sine Wave
>Oscillator" on page 8, right side, using an incandescent bulb
>(Eldema 1869, with about 100k hr lifetime.)

Sorry, forgot to add that page 11 shows amplitude
stabilization using 2 BJTs and a JFET.

Jon	

On Aug 27, 1:30=A0am, Tim Wescott <t...@seemywebsite.com> wrote:
> On Thu, 25 Aug 2011 20:29:45 -0700, Bill Sloman wrote:
> > On Aug 26, 5:26=A0am, Tim Wescott <t...@seemywebsite.com> wrote:
> >> On Wed, 24 Aug 2011 21:53:24 -0700,BillSlomanwrote:
> >> > On Aug 25, 3:24=A0am, Tim Wescott <t...@seemywebsite.com> wrote:
> >> >> On Wed, 24 Aug 2011 05:15:09 -0700,BillSlomanwrote:
> >> >> > On Aug 24, 7:22=A0pm, davew <david.wo...@gmail.com> wrote:
> >> >> >> I'm searching for a simple one chip solution if anyone has any
> >> >> >> ideas. Best I've found so far might be the old 8038 function
> >> >> >> generator chip.
>
> >> >> > If you are restricted to one chip, this is probably as good as it
> >> >> > gets. It distorts a triangular wave to a tolerable approximation
> >> >> > to a sine wave.
>
> >> >> > You can do better by feeding a square wave through a shift
> >> >> > register clock at some convenient multiple of the square wave
> >> >> > frequency, tying a series of resistors to the outputs of the shif=
t
> >> >> > register and summing the currents through the resistors into a
> >> >> > virtual earth to produce a staircase approximation to a sine wave=
,
> >> >> > but it takes quite a long shift register and quite a few close
> >> >> > tolerance resistors to do better than the 8038, and =A0it's still=
 a
> >> >> > three chip solution - basically a programmable logic device to
> >> >> > provide the shift register and the dividers to generate the squar=
e
> >> >> > wave, the VCO to to generate the clock at some fairly high
> >> >> > multiple of the output frequency, and an op amp to sum the
> >> >> > currents from the resistors, plus you have to find board space fo=
r
> >> >> > the resistors.
>
> >> >> > The Analog Devices DDS chips do provide a very good one chip
> >> >> > solution - the more expensive chips include 14-bit DACs - but it
> >> >> > isn't an analog solution.
>
> >> >> How about a CD4040 and a bunch of resistors? =A0(I think I mean the
> >> >> CD4040 -- the 4020, 4040, and 4060 are all big-ass counters, one of
> >> >> which has an oscillator built in).
>
> >> >> It's a ripple counter, but if you're going slow enough the clock
> >> >> glitches shouldn't get you too bad.
>
> >> > Well, the CD4040 is cheap, but a progammable logic device can provid=
e
> >> > the same funcion - and a lot more beside - in a single chip, which i=
s
> >> > one of the things the OP is asking for.
>
> >> > And the CD4040 is slow - slow enough for it to be nuisance when I
> >> > first used the part back in 1975. It looks glacial these days.
>
> >> At one point you could get 74HC4040 parts -- dunno if they're still ou=
t
> >> there.
>
> >> I was thinking of that part because of the built-in oscillator -- what
> >> programmable logic part has that?
>
> >http://www.datasheetcatalog.org/datasheet/philips/74HC4040.pdf
>
> > Some of the biggish CMOS counters RCA made at that time had built-in
> > oscillator drivers, but the 4040 wasn't one of them.
>
> Then -- as I stated in my original reply -- it's either the 4020 or the
> 4060

It was the 4060

http://www.futurlec.com/4000Series/CD4020.shtml

as if anybody cared. The original poster clearly isn't interested in
going down that route, and if he were he'd be more likely to go for a
programmable logic device which could provide all the logic he wanted
- including providing the gates to activate a simple oscillator - in a
single chip.

Sadly, he doesn't want to think about digitally-based solutions.

--
Bill Sloman, Nijmegen

On Thu, 25 Aug 2011 14:25:22 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

For the love of Jobs will you PLEASE learn how to snip.  PLEASE.

Jim

For the love of Jobs will you PLEASE learn how to snip.  PLEASE.

Jim

RST Engineering wrote:

> For the love of Jobs will you PLEASE learn how to snip.  PLEASE.
> 
> Jim
Ok,  you can stop stuttering now, I heard you the first time..

  Jamie

On Sat, 27 Aug 2011 19:44:12 -0700, RST Engineering
<jweir43@gmail.com> wrote:

>For the love of Jobs will you PLEASE learn how to snip.  PLEASE.
>
>Jim

His entire post was only 25 lines!

John

John Larkin wrote:

> On Sat, 27 Aug 2011 19:44:12 -0700, RST Engineering
> <jweir43@gmail.com> wrote:
> 
> 
>>For the love of Jobs will you PLEASE learn how to snip.  PLEASE.
>>
>>Jim
> 
> 
> His entire post was only 25 lines!
> 
> John
> 
Hell, that's nothing, just getting warmed up

  Jamie