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Emitter Follower + LPF Sine Convert for CD4060

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ate-variable filter for a Butterworth when you can use 1 op-amp either. Loo ks like its been designed by a physicist or some non engineer with a basic electronics knowledge.

R or not it is non standard and daft. Also that state filter is not really a state filter. It is just two first orders in cascade with feedback. A pro per state feedback filter has two integrators with feedback of a defined am ount as per a signal flow graph. It is a filter but not a standard one and pointless. Looks like its been designed by a physicist or student.

I wouldn't built a state filter for a second order low pass full stop. The extra op-amps just generate noise. yes they have advantages because you can swap components easily but these are outweighed by the complexity. A Salen Key or Multiple Feedback will do the job fine. However, in todays w orld, unless it is an anti-aliasing filter (and you need fewer of these to o with Sigma-delta ADCs) then you should go digital wherever possible. Gett ing linear phase is too fiddly in analogue.

The circuit you have is a well known circuit in all the text books and is o ften used a a first example before leading to more complex designs. It is n ot a state-variable filter in the common sense at least. In a state-variabl e filter the states are defined first. In your case I don't even know what the states are though I suppose you can work them out. As for scaling, that 's not a problem either for a few op-amps.

Reply to
gyansorova
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[snip the googlism crap]

Citation? I've never seen it in a text book. I first devised it in the 1970-73 timeframe when I was making hybrid (thick-film) filters for the telephone industry.

Your take on the world seems all related to digitally-implemented versions.

You can't do complex functions with Sallen-Key configurations due to the component sensitivities exacerbated by Q. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Actually, =/= is unity, or something. Do you mean MultiSim != PSpice? Or, maybe MultiSim PSpice?

Reply to
John S

From memory, MultiSim took Berkely's SPICE program and adapted it to run on PC, thus the new name, PSpice. MultiSim published an 'in-depth' manual which cost over $100 and was WELL worth the money.

Then I think, MultiSim was bought out by PCad? and then the division or the whole thing was bought by OrCAD. I do remember at each sale, people commenting on how PSpice was ruined, and then really ultimately ruined by OrCAD.

I do know that OrCAD leaves some VERY large nuisance bugs in their programs. One bug in their layout software which uses Schematic Capture is still going strong up into version 16 had absolutely NO workaround and drove me nuts! A combination of errors in the Library and transferring proprietary info. I was told by OrCAD personnel that MANY people complained and they didn't understand why it wasn't changed/addressed in some way. These types of experiences simply reinforces exactly why I don't buy software. And only write my own, or get it free somewhere.

Reply to
RobertMacy

MicroSim =/= MultiSim

MicroSim =/= OrCAD. I still use the original crispy flavor MicroSim (PSpice) Schematics, and design ASIC's on my laptop with it all the time ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

What really pisses me off is people who call bug fixes "upgrades", and expect you to pay for them.

I wish I could get away with that ;-)

--
"Design is the reverse of analysis" 
                   (R.D. Middlebrook)
Reply to
Fred Abse

into

Exar

Thanks for catching my typo.

Reply to
josephkk

You can make a power MOSFET oscillator that will generate a near perfect sine wave..

you would need 1 coil from supply to DRAIN, 2 caps, 1 from Drain to Source and the other from source to common. The source would of course have a resistor there so the MOSFET beoomes linear.

Vcc supply

  • | | +----------+ | C| | C|100mh + C| .-. + 5k | | | | | | '-' +-------+ ++ | | | ||-+ | | ||
Reply to
Maynard A. Philbrook Jr.

Just curious. How much does a 100mH inductor and two 500uF capacitors cost compared to say....a microController chip?

last time I bought big value caps they were on the order of a couple of dollars each and even small value inductors [wound somewhere by obviously tiny people] were close to $5

but in comparison, I could get a PIC type thingy for $1 !!

how much is TI's MPS430?

or Altera's FPGA's?

I am OLD School analog designer, but there's a LOT of economic pressure out there to go digital.

Reply to
RobertMacy

No problem. Some just jump out at me. At least I just point them out, without ridiculing people for them. :)

--
Anyone wanting to run for any political office in the US should have to 
have a DD214, and a honorable discharge.
Reply to
Michael A. Terrell

But it will never produce a smooth sinewave with no switching noise.

That said, the vast volume taken up by those parts would easily be filled in with the filtering necessary to get a better result (no clipping).

One could even eliminate the uC altogether and build a Wein bridge type from the same filter components, achieving arbitrarily low distortion depending on AGC method.

Tim

--
Seven Transistor Labs 
Electrical Engineering Consultation 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

ost compared to say....a microController chip?

dollars each and even small value inductors [wound somewhere by obviousl y tiny people] were close to $5.

in with the filtering necessary to get a better result (no clipping).

rom the same filter components, achieving arbitrarily low distortion depend ing on AGC method.

The whole thing is supposed to run from a 6V battery - four AAA cells. Wein bridges aren't the lowest current option when it comes to generating a low distortion sine wave, and buffering the output so that it can feed up to 50mA at 5V peak-to-peak into an optical array and still offer low distor tion is getting a bit silly.

A uC producing one of Don Lancaster's "magic sinewave" binary sequences doe sn't need much filtering - the high frequency components can be essentially zero up to about the 20th harmonic and a simple low-pass will get rid of t he higher harmonic content. You need rather long sequences to do that well, but at 16kHz this isn't difficult. When I looked at them for synthesising a 15kHz sinewave this wasn't true.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

What's not low power about a Wein bridge? Run it at arbitrarily low amplitude, and high impedance, and use micro/nanopower op-amps. You want high impedance anyway to keep the C small (hopefully using chip C0Gs or whatever for stability).

That kind of drive and distortion (I guess you're talking < 0.01% levels here..?) needs a buffer anyway. Not going to get that with the nonlinearity in a uC's output pins (non-ohmic switches, unequal pull-up and pull-down resistances; switching time differences and skew).

Er, 16 *Hz*, not kHz. Even easier! Getting the timing right at 16k might be a bit of a challenge, but pretty much any uC could bit-bang that kind of timing for 16Hz, at least.

I don't see how you'd be doing it without a buffer and more-or-less class AB level power consumption. You might have some luck with an ADC and feedback, doing sigma-delta something or other (the low-distortion sine table would take up a bit of memory, and the computation would require some baseline uC, probably nothing an Arduino or higher couldn't cope with). In which case you could get by with a relatively high distortion switcher something or other for the amp.

I don't think it's been stated if the optical array is capacitive, resistive or what (or I just don't know the obvious). A capacitive load of course would draw very little power if driven by a class D amp.

Tim

--
Seven Transistor Labs 
Electrical Engineering Consultation 
Website: http://seventransistorlabs.com
Reply to
Tim Williams 

--
Snipped LTspice circuit list
Reply to
John Fields 

--
I didn't know LTspice ran on a Commodore 64.
Reply to
John Fields

Wein bridges aren't the lowest current option when it comes to generating a low distortion sine wave, and buffering the output so that it can feed up to 50mA at 5V peak-to-peak into an optical array and still offer low disto rtion is getting a bit silly.

The amplifier that offer low distortion.

amplitude, and high impedance, and use micro/nanopower op-amps. You want high impedance anyway to keep the C small (hopefully using chip C0Gs or wh atever for stability).

Best of luck with that.

here..?) needs a buffer anyway. Not going to get that with the nonlinear ity in a uC's output pins (non-ohmic switches, unequal pull-up and pull-dow n resistances; switching time differences and skew).

You can buy fairly high quality - and fairly fast - analog switches, which do minimise these sources of non-linearity.

The OP is - fairly clearly - not expecting to keep the harmonics down to 0.

01% levels (-80dB). He says that he'd be happy with a well-round square wav e, and didn't reject John Larkin's single pole filter out of hand.

doesn't need much filtering - the high frequency components can be essenti ally zero up to about the 20th harmonic and a simple low-pass will get rid of the higher harmonic content. You need rather long sequences to do that well, but at 16Hz this isn't difficult. When I looked at them for synthesis ing a 15kHz sinewave this wasn't true.

Obviously. A particularly embarrassing typo to make and even more embarrass ing to miss.

ge, but pretty much any uC could bit-bang that kind of timing for 16Hz, at least.

AB level power consumption. You might have some luck with an ADC and feed back, doing sigma-delta something or other (the low-distortion sine table w ould take up a bit of memory, and the computation would require some baseli ne uC, probably nothing an Arduino or higher couldn't cope with). In which case you could get by with a relatively high distortion switcher something or other for the amp.

I like the resistor-tapped shift register version of the FIR filter for get ting a decent sine wave out of a square wave. If you do too many taps, you end up needing three resistors - with the last one selected to take out the tolerances on the other two - to get the accuracy, but it does work very w ell.

ive or what (or I just don't know the obvious). A capacitive load of cours e would draw very little power if driven by a class D amp.

I doubt if the OP knows enough about what he's doing to tell us. His respon ses haven't demonstrated a particularly high level of technical insight. An d people who are in the business of re-inventing the lumpy roller tend to b e wary of disclosing their trade secrets.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

'Wien'. The guy's name was Max Wien, not Wein. He was a German physicist born in 1866.

Jeroen Belleman

Reply to
Jeroen Belleman

e from the same filter components, achieving arbitrarily lowdistortion depe nding on AGC method.

Wien bridges aren't ...

born in 1866.

emitic, which was probably praise, since in 1938 in Jenna (when he died) he would have been expected to be violently anti-Semitic.

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Bill Sloman, Sydney
Reply to
Bill Sloman

It sims very fast on my PC.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation
Reply to
John Larkin

Oops. I should know better about my i's and e's. There's even a Steiner in my family. Hey, wait a minute... :)

Tim

--
Seven Transistor Labs 
Electrical Engineering Consultation 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

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