Forums

oscillator with constant amplitude

Started by Tom Del Rosso August 5, 2015
I don't want anybody to design it for me, but in general how would you 
make an oscillator with a sine output of constant amplitude over a range 
of supply voltage (let's say the operating range of the op-amp).  What I 
have in mind is a battery supply, but with no power wasted in a 
regulator.  Sure the oscillator would also waste power but not as much. 
Would a square output be simpler?

-- 


On Wed, 05 Aug 2015 12:39:09 -0400, Tom Del Rosso wrote:

> I don't want anybody to design it for me, but in general how would you > make an oscillator with a sine output of constant amplitude over a range > of supply voltage (let's say the operating range of the op-amp). What I > have in mind is a battery supply, but with no power wasted in a > regulator. Sure the oscillator would also waste power but not as much. > Would a square output be simpler?
I would use AGC. If wasting power is an issue then you're going about it more or less backwards -- at best, a linear oscillator on an unregulated rail with a constant output is going to use just as much power as an oscillator being powered through a linear regulator -- and it'll probably be worse. If you can run at a constant amplitude, use a switching regulator. What frequency range are you looking at? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso"
<fizzbintuesday@that-google-mail-domain.com> wrote:

>I don't want anybody to design it for me, but in general how would you >make an oscillator with a sine output of constant amplitude over a range >of supply voltage (let's say the operating range of the op-amp). What I >have in mind is a battery supply, but with no power wasted in a >regulator. Sure the oscillator would also waste power but not as much. >Would a square output be simpler?
Here's a simple-minded one... <http://www.analog-innovations.com/SED/GyratorFilter_A1A_Oscillator.pdf> ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso"
<fizzbintuesday@that-google-mail-domain.com> wrote:

>I don't want anybody to design it for me, but in general how would you >make an oscillator with a sine output of constant amplitude over a range >of supply voltage (let's say the operating range of the op-amp). What I >have in mind is a battery supply, but with no power wasted in a >regulator. Sure the oscillator would also waste power but not as much. >Would a square output be simpler?
A square wave could be made extremely stable; generate it from CMOS logic powered by a voltage regulator. The supply current would be almost entirely the load current, so the regulator really doesn't waste power.
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in 
message news:hbh4satpp249v8ie3612nn6h2uv26ss0of@4ax.com...
> On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso" > <fizzbintuesday@that-google-mail-domain.com> wrote: > >>I don't want anybody to design it for me, but in general how would you >>make an oscillator with a sine output of constant amplitude over a range >>of supply voltage (let's say the operating range of the op-amp). What I >>have in mind is a battery supply, but with no power wasted in a >>regulator. Sure the oscillator would also waste power but not as much. >>Would a square output be simpler? > > Here's a simple-minded one... > > <http://www.analog-innovations.com/SED/GyratorFilter_A1A_Oscillator.pdf> > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | San Tan Valley, AZ 85142 Skype: skypeanalog | | > | 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.
What do D5 and D6 do? Are they supposed to be back to back? I can see if they were zeners but 4148s?
On Wed, 5 Aug 2015 13:46:42 -0400, "Tom Miller"
<tmiller11147@verizon.net> wrote:

> >"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in >message news:hbh4satpp249v8ie3612nn6h2uv26ss0of@4ax.com... >> On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso" >> <fizzbintuesday@that-google-mail-domain.com> wrote: >> >>>I don't want anybody to design it for me, but in general how would you >>>make an oscillator with a sine output of constant amplitude over a range >>>of supply voltage (let's say the operating range of the op-amp). What I >>>have in mind is a battery supply, but with no power wasted in a >>>regulator. Sure the oscillator would also waste power but not as much. >>>Would a square output be simpler? >> >> Here's a simple-minded one... >> >> <http://www.analog-innovations.com/SED/GyratorFilter_A1A_Oscillator.pdf> >> >> ...Jim Thompson >> -- >> | James E.Thompson | mens | >> | Analog Innovations | et | >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >> | San Tan Valley, AZ 85142 Skype: skypeanalog | | >> | 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. > >What do D5 and D6 do? Are they supposed to be back to back? I can see if >they were zeners but 4148s? > > >
Miniscule amount of capacitance... in other words... a hack quickly thrown together. In practice I'd probably use a diff-pair with controlled tail current derived from measuring the amplitude... something simple like... <http://www.analog-innovations.com/SED/VCOwithAGC.pdf> >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Age gets better with wine!
On Wed, 5 Aug 2015, Jim Thompson wrote:

> On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso" > <fizzbintuesday@that-google-mail-domain.com> wrote: > >> I don't want anybody to design it for me, but in general how would you >> make an oscillator with a sine output of constant amplitude over a range >> of supply voltage (let's say the operating range of the op-amp). What I >> have in mind is a battery supply, but with no power wasted in a >> regulator. Sure the oscillator would also waste power but not as much. >> Would a square output be simpler? > > Here's a simple-minded one... > > <http://www.analog-innovations.com/SED/GyratorFilter_A1A_Oscillator.pdf> >
What about the 1648 ECL VCO, that had built in AGC? Michael
On Wed, 5 Aug 2015 12:39:09 -0400, "Tom Del Rosso"
<fizzbintuesday@that-google-mail-domain.com> wrote:

>I don't want anybody to design it for me, but in general how would you >make an oscillator with a sine output of constant amplitude over a range >of supply voltage (let's say the operating range of the op-amp). What I >have in mind is a battery supply, but with no power wasted in a >regulator. Sure the oscillator would also waste power but not as much. >Would a square output be simpler?
ICL8038 or similar triangle wave generator with built in triangle to sine converter ?
More responses than I expected.  I appreciate it but can't respond to 
all right now.

Tim Wescott wrote:
> > I would use AGC. > > If wasting power is an issue then you're going about it more or less > backwards -- at best, a linear oscillator on an unregulated rail with > a constant output is going to use just as much power as an oscillator > being powered through a linear regulator -- and it'll probably be > worse.
I understand what you mean. The idea came that it must be possible, but I've never seen it done specifically, so I got curious about how complex such an oscillator would be. More complex than a regulator it turns out.
> If you can run at a constant amplitude, use a switching regulator. > > What frequency range are you looking at?
Low KHz. --
On 06/08/15 17:03, Tom Del Rosso wrote:
> More responses than I expected. I appreciate it but can't respond to > all right now. > Tim Wescott wrote: >> I would use AGC. >> If wasting power is an issue then you're going about it more or less >> backwards -- at best, a linear oscillator on an unregulated rail with >> a constant output is going to use just as much power as an oscillator >> being powered through a linear regulator -- and it'll probably be >> worse. > I understand what you mean. The idea came that it must be possible, but > I've never seen it done specifically, so I got curious about how complex > such an oscillator would be. More complex than a regulator it turns > out.
Here's an example of an oscillator (for 3.6MHz) that uses AGC. It's not very complicated, though it's unsuitable for "Low KHz" because of the size of the inductor you need. If you want to run it, you'll need to supply a transistor model, as I didn't include my library part (and you might need to change some resistor values for the AGC to work). But I suspect you'll be able to see how it works without doing that (use LTSpice to view!) Clifford Heath. Version 4 SHEET 1 1952 708 WIRE 304 -336 192 -336 WIRE 752 -336 304 -336 WIRE 192 -288 192 -336 WIRE 192 -176 192 -208 WIRE 192 -176 -64 -176 WIRE 432 -176 192 -176 WIRE 528 -176 432 -176 WIRE 192 -144 192 -176 WIRE 304 -96 304 -336 WIRE 752 -96 752 -336 WIRE -48 -48 -64 -48 WIRE 32 -48 -48 -48 WIRE 96 -48 32 -48 WIRE 192 -48 192 -64 WIRE 192 -48 160 -48 WIRE 240 -48 192 -48 WIRE 432 -48 432 -176 WIRE 32 112 32 -48 WIRE 96 112 32 112 WIRE 640 112 160 112 WIRE 32 208 32 112 WIRE 528 208 528 -176 WIRE 432 304 432 32 WIRE -48 320 -48 -48 WIRE 32 352 32 272 WIRE 304 352 304 0 WIRE 304 352 32 352 WIRE 368 352 304 352 WIRE 192 400 192 -48 WIRE 304 400 304 352 WIRE 32 416 32 352 WIRE -48 528 -48 400 WIRE 32 528 32 480 WIRE 32 528 -48 528 WIRE 192 528 192 480 WIRE 192 528 32 528 WIRE 304 528 304 480 WIRE 304 528 192 528 WIRE 432 528 432 400 WIRE 432 528 304 528 WIRE 528 528 528 272 WIRE 528 528 432 528 WIRE 752 528 752 -16 WIRE 752 528 528 528 WIRE 752 544 752 528 FLAG 752 544 0 FLAG -64 -48 Vosc IOPIN -64 -48 Out FLAG -64 -176 Vbias IOPIN -64 -176 Out FLAG 640 112 Vout IOPIN 640 112 Out SYMBOL voltage 752 -112 R0 WINDOW 123 24 126 Left 2 WINDOW 39 24 111 Left 2 SYMATTR InstName V1 SYMATTR Value 3.2v SYMBOL cap 16 208 R0 SYMATTR InstName C1 SYMATTR Value 150pf SYMBOL cap 16 416 R0 SYMATTR InstName C2 SYMATTR Value 2.2nF SYMBOL ind -64 304 R0 SYMATTR InstName L3 SYMATTR Value 15&micro;H SYMBOL npn 240 -96 R0 SYMATTR InstName Q1 SYMATTR Value CA3046 SYMBOL res 176 -160 R0 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL npn 368 304 R0 SYMATTR InstName Q2 SYMATTR Value CA3046 SYMBOL res 176 -304 R0 SYMATTR InstName R2 SYMATTR Value 47k SYMBOL cap 512 208 R0 SYMATTR InstName C4 SYMATTR Value 2.2n SYMBOL res 288 384 R0 SYMATTR InstName R6 SYMATTR Value 2.2k SYMBOL cap 160 -64 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 10pF SYMBOL res 176 384 R0 SYMATTR InstName R3 SYMATTR Value 100k SYMBOL res 416 -64 R0 SYMATTR InstName R8 SYMATTR Value 10k SYMBOL cap 160 96 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 3.3pF TEXT 320 576 Left 2 !.tran 0 200uS 0 1nS TEXT -160 576 Left 2 !.inc "..\\Lib\\Transistors\\ca3000.lib"