Can someone please direct me to a passive circuit using breakpoint diodes, preferably no more than six, to shape a sine wave from a 5Vpp triangle? The available power source is single supply 6V.
I did check the net, but had no luck with finding a basic approach.
Mike Kendall
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
The ICL8038 function generator IC had a workable design, albeit involving transistors. Its 'sine waves' didn't look too bad either.
Chris
It comes to mind to use comparators ala Don Lancaster. Surf his pages.
...Jim Thompson
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Take a look at the old Wavetek function generators e.g.
The voltage this circuit uses is higher (+/- 15) and it uses a set of
8 diodes (presumably matched). You may be able to Spice up a version which will work to meet your needs.
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Yes, but I am looking for a similar approach that will work off of my specified 6V single rail supply.
The only ones I could find using diodes-passives were +/-, and higher supply voltage, as you indicate.
Mike
"Mike Kendall"
** I think you are outa luck with that approach with such a restricted supply.Think of using an active filter instead.
You have not said what frequency range you need, but as there are only odd numbered harmonics to suppress it might be quite easy.
...... Phil
If you use schottky-diodes, you might come along with such a low supply voltage. The question is what you need this circuit for. If the signal is to be differentiated, diodes with there turnpoints are usually not suitable. You could use a differential amp with two transistors, of which the tanh function is close to a sin for values of ^Ve =3D 2.8Vt=3D
72mV. This gives an absolut error of 3% max. THD would be 1.6%. With 2 additional diodes for the peak, you can come down to 0.4% THD. ciao Ban Apricale, Italy
I have a demo circuit as a part of an LTSpice tutorial. It is titled Funcgen, I think. Here is the download link:
On 11 Jun, 00:33, Mike Kendall wrote:
This is an LTspice drawing. 6 diodes and a 6V supply. Gives a clean 5V sine out for a 5V triangle in. O/p distortion is sensitive to the pkpk voltage at R8,R7 junction. It's usual to put a pot in here to adjust for cleanest sine. (pot down to about +/- 200mV)
Version 4 SHEET 1 1328 680 WIRE 304 -192 176 -192 WIRE 464 -192 304 -192 WIRE 544 -192 464 -192 WIRE 176 -176 176 -192 WIRE 304 -80 304 -112 WIRE 400 -80 304 -80 WIRE 544 -80 544 -112 WIRE 544 -80 480 -80 WIRE 640 -80 544 -80 WIRE 720 -80 704 -80 WIRE 304 -32 304 -80 WIRE 544 -32 544 -80 WIRE 800 -32 768 -32 WIRE 912 -32 880 -32 WIRE -32 80 -160 80 WIRE 64 80 -32 80 WIRE 176 80 144 80 WIRE 304 80 304 32 WIRE 304 80 176 80 WIRE 544 80 544 32 WIRE 544 80 304 80 WIRE 720 80 720 -80 WIRE 768 80 768 -32 WIRE 768 80 720 80 WIRE 816 80 768 80 WIRE 912 96 912 -32 WIRE 912 96 880 96 WIRE 992 96 912 96 WIRE 176 112 176 80 WIRE 816 112 800 112 WIRE -160 128 -160 80 WIRE 304 144 304 80 WIRE 800 144 800 112 WIRE 544 160 544 80 WIRE 304 272 304 208 WIRE 400 272 304 272 WIRE 544 272 544 224 WIRE 544 272 480 272 WIRE 656 272 544 272 WIRE 720 272 720 80 WIRE 304 304 304 272 WIRE 544 320 544 272 WIRE 304 400 304 384 WIRE 304 400 176 400 WIRE 416 400 304 400 WIRE 544 400 416 400 WIRE 176 416 176 400 FLAG 464 -192 pos FLAG 416 400 neg FLAG 176 496 0 FLAG 176 -96 0 FLAG -160 208 0 FLAG -32 80 triangle FLAG 992 96 sine-out FLAG 176 192 0 FLAG 848 64 pos FLAG 848 128 neg FLAG 800 144 0 SYMBOL voltage 176 -192 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 3 SYMBOL voltage 176 400 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value -3 SYMBOL diode 288 -32 R0 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL voltage -160 112 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(-2.5 2.5 0 500u 500u 0 1m) SYMATTR InstName V3 SYMBOL diode 288 144 R0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL diode 528 -32 R0 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL diode 640 -64 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D4 SYMATTR Value 1N4148 SYMBOL diode 528 160 R0 SYMATTR InstName D5 SYMATTR Value 1N4148 SYMBOL diode 720 256 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D6 SYMATTR Value 1N4148 SYMBOL res 288 -208 R0 SYMATTR InstName R1 SYMATTR Value 8.2k SYMBOL res 528 -208 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL res 496 -96 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 150 SYMBOL res 496 256 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 150 SYMBOL res 320 400 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R5 SYMATTR Value 8.2k SYMBOL res 560 416 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL res 160 96 R0 SYMATTR InstName R7 SYMATTR Value 120 SYMBOL res 160 64 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R8 SYMATTR Value 1k SYMBOL Opamps\\\\1pole 848 96 R0 SYMATTR InstName U1 SYMATTR Value2 Avol=1Meg GBW=1Meg Slew=1Meg SYMBOL res 896 -48 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R10 SYMATTR Value 4k7 TEXT -16 248 Left 0 !.tran 0 10m 0 50n
Patent:3737642 shows one way to do it.
General question comes to mind... has anyone written a program that would derive the "best" piecewise linear fit to a function, f(x), for a given number of segments?
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
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America: Land of the Free, Because of the Brave
Dear John,
This looks perfect, but I can't get it to run in LTSpice. A window comes up saying "Multiple instances of symbol", etc.
I am not a regular user of this program. Any chance of providing an asc. file or please suggest some other remedy?
Would be sincerely appreciated.
Mike Kendal
Mike,
Highlight everything in John's post from (and including) Version 4 to the last line. Paste it into notepad, and save it as diodeshaper.asc Don't forget to change the "Save as Type" box in notepad to all files.
Then use LTSpice to run it.
Ed
For *diode shapers*? Wow, great idea, I'll get right on it, as soon as I finish my .NET visualization tool for helping pigs decide on their lipstick colour. ;)
If you really want to do this, you can kluge it up pretty fast from a singular value decomposition routine, e.g. SVDFIT from Numerical Recipes, with an optimization loop that moves the fit points around to minimize the residual. For linear fits, you use a set of triangular eigenfunctions, each of which goes from 0 at point m-1 to 1 at point m to 0 again at point m+1. Any piecewise linear approximation is a weighted sum of those.
I did this a couple of months ago with cubic splines for a tunnel junction parameter extraction program--it needed speeding up so I could generalize it to finite temperature, which takes a lot more computation. The spline bit took about half a day, and it works great, but I have to go back and finish debugging the finite-temperature part. :(
Cheers,
Phil Hobbs
Cheers,
Phil Hobbs
My approach to "diode shapers" uses OpAmps, so I don't have to contend with diode vagaries.
"Numerical Recipes", the book I presume? I think I've opened it once or twice since I bought it a very long time ago ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Sometimes I envy you all the transistors you can use. Here I spend years just trying to make one or two useful devices, and all the while, you're squandering them on breakpoint amplifiers. ;)
Widlar (iirc) published a cute trick using BJT saturation for making breakpoint amplifiers--you run a bunch of emitter followers whose bases connect to the summing junction, and their emitters to the output via resistors, with collector resistors to some appropriate reference. When a transistor saturates, its beta drops to zilch, and the emitter resistor suddenly appears in parallel with the feedback resistor. It's reasonably temperature independent because the switchover depends on VCE instead of VBE, and it has much sharper edges than a garden-variety diode breakpoint amp.
Yes, it's a pretty good book attached to some reasonably functional although sometimes ugly code. I built a shared library out of it some years back, because (unlike most other numerical codes I've seen) NR's documentation quality is excellent and the number of actual bugs is quite small.
Cheers,
Phil Hobbs
Yes, a long time ago. I've also used Excel, believe it or not. Mathematicians tend to define "best" in terms of least squares, but often (at least in instrumentation design) what you want to minimize is the maximum abs. value of error everywhere within a range. I have access to Mathcad these days, so I might try that if Excel didn't work. Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Least squares _would_ get messy. I'll try Excel. PSpice can do it but it's a tedious process of tweak-tweak-tweak :-(
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
See...
Newsgroups: alt.binaries.schematics.electronic Subject: Tri to Sine diode shaper (from S.E.D) - BestFitPiecewiseLinear.pdf Message-ID:
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
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