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Oscillator Proposal

Started by Jim Thompson March 14, 2015
Oscillator Proposal...

Suppose I have a series RLC, one end grounded, the other end driven by
a chip, how might I make that into an oscillator?

All wild ideas accepted... this is for a custom chip.
		
                                        ...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.
Den l�rdag den 14. marts 2015 kl. 18.07.58 UTC+1 skrev Jim Thompson:
> Oscillator Proposal... > > Suppose I have a series RLC, one end grounded, the other end driven by > a chip, how might I make that into an oscillator? > > All wild ideas accepted... this is for a custom chip. >
can you measure the drive current ? rearrange something like this, https://c2.staticflickr.com/4/3573/3491130929_0791bd8201.jpg -Lasse
On 3/14/2015 1:07 PM, Jim Thompson wrote:
> Oscillator Proposal... > > Suppose I have a series RLC, one end grounded, the other end driven by > a chip, how might I make that into an oscillator? > > All wild ideas accepted... this is for a custom chip. > > ...Jim Thompson >
Series RLC is harder than parallel, because to leading order there's no signal on the pin at resonance. (If it were parallel, you could do a single-ended version of the MC1648, which you may have heard of.) ;) You need to arrange a negative resistance at the pin, which isn't hard to do, and use the AC current to drive the next stage. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Sat, 14 Mar 2015 10:16:46 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>Den l&#2013266168;rdag den 14. marts 2015 kl. 18.07.58 UTC+1 skrev Jim Thompson: >> Oscillator Proposal... >> >> Suppose I have a series RLC, one end grounded, the other end driven by >> a chip, how might I make that into an oscillator? >> >> All wild ideas accepted... this is for a custom chip. >> > >can you measure the drive current ? > >rearrange something like this, https://c2.staticflickr.com/4/3573/3491130929_0791bd8201.jpg > > >-Lasse
Yep, that's the general direction I've been heading, observe the drive current and switch at zero crossings... with some minimum current latch-out flip-flop to make sure it starts. ...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 Sat, 14 Mar 2015 13:36:39 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 3/14/2015 1:07 PM, Jim Thompson wrote: >> Oscillator Proposal... >> >> Suppose I have a series RLC, one end grounded, the other end driven by >> a chip, how might I make that into an oscillator? >> >> All wild ideas accepted... this is for a custom chip. >> >> ...Jim Thompson >> > >Series RLC is harder than parallel, because to leading order there's no >signal on the pin at resonance. (If it were parallel, you could do a >single-ended version of the MC1648, which you may have heard of.) ;)
Gee! That part number sure sounds familiar ;-)
> >You need to arrange a negative resistance at the pin, which isn't hard >to do, and use the AC current to drive the next stage. > >Cheers > >Phil Hobbs
I was fretting over not wanting a DC path to ground, but maybe that can be minimized. ...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 3/14/2015 2:13 PM, Jim Thompson wrote:
> On Sat, 14 Mar 2015 13:36:39 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 3/14/2015 1:07 PM, Jim Thompson wrote: >>> Oscillator Proposal... >>> >>> Suppose I have a series RLC, one end grounded, the other end driven by >>> a chip, how might I make that into an oscillator? >>> >>> All wild ideas accepted... this is for a custom chip. >>> >>> ...Jim Thompson >>> >> >> Series RLC is harder than parallel, because to leading order there's no >> signal on the pin at resonance. (If it were parallel, you could do a >> single-ended version of the MC1648, which you may have heard of.) ;) > > Gee! That part number sure sounds familiar ;-) > >> >> You need to arrange a negative resistance at the pin, which isn't hard >> to do, and use the AC current to drive the next stage. >> >> Cheers >> >> Phil Hobbs > > I was fretting over not wanting a DC path to ground, but maybe that > can be minimized. > > ...Jim Thompson >
Well, if it's series, you can bias the pin anyplace you like. All sorts of RF parts do that, e.g. the AD9956 DDS/PLL chip, which I'm working with at the moment. I had to dig out the demo board schematic to figure out how to drive all the differential inputs...the datasheet is a vast wasteland. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Am 14.03.2015 um 18:16 schrieb Lasse Langwadt Christensen:
> Den l&#2013266168;rdag den 14. marts 2015 kl. 18.07.58 UTC+1 skrev Jim Thompson: >> Oscillator Proposal... >> >> Suppose I have a series RLC, one end grounded, the other end driven by >> a chip, how might I make that into an oscillator? >> >> All wild ideas accepted... this is for a custom chip. >> > > can you measure the drive current ? > > rearrange something like this, https://c2.staticflickr.com/4/3573/3491130929_0791bd8201.jpg
I cannot see the start of the thread??? That calls for the circuit that most VHF VCOs use. Connect the base of a CC stage to the RLC. Emitter resistor is usually relatively large and loaded with some C. That creates the equivalent of a negative R and a small capacitor if one looks into the base. Oscillates like hell. Drawback is the area for the capacitor or a pin for an external one. regards, Gerhard
Done it many times, as an industrially important process: drive it with a 
voltage and phase lock on current.  Or for a general resistance source 
(rather than ideal voltage source), you'll assume drive voltage (internal 
clock) and measure the pin voltage to infer current.  Under the 
restriction Rds(on) < sqrt(L/C), but not by too much, so that the signal 
is not too small, nor the Q too low.

This will likely restrict what range of L, C can be used, since you get Q 
* VCC volts on them and Rds(on) ~ 50 ohms for average HC scale CMOS.  And 
I(pin) < 10mA or whatever, and probably quite a bit below that if it's a 
low power application.

Maybe not as bad if it's a low voltage CMOS process where you can get low 
resistance cheaply, but then you need another supply (but hey... maybe 
make it variable and add AGC?).  Or maybe it's reasonable to build a low 
impedance analog output pin, so the amplitude is small (optionally 
variable), and low impedance.

You could also do what every crystal ever does: add a loading cap, so your 
circuit effectively spans a capacitive divider that's part of the resonant 
capacitor.  Crystals having the unique distinction of extremely large 
inductance and extremely small capacitance (the motional equivalent 
components), so that the impedance is still rather high (~kohms); a low 
impedance resonator would need a respectively large loading cap.

If you need a "discrete"* style oscillator (a few transistors and 
resistors rather than an entire loop), it should be fruitful to look at 
the V-I transform of a traditional parallel resonant circuit.

*Funny way to put it, since it's going inside a chip...

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote 
in message news:hiq8ga91b24hlsji1oh7rnbv7bm0nct23t@4ax.com...
> Oscillator Proposal... > > Suppose I have a series RLC, one end grounded, the other end driven by > a chip, how might I make that into an oscillator? > > All wild ideas accepted... this is for a custom chip. > > ...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 Sat, 14 Mar 2015 10:07:50 -0700, Jim Thompson  
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

> Oscillator Proposal... > > Suppose I have a series RLC, one end grounded, the other end driven by > a chip, how might I make that into an oscillator? > > All wild ideas accepted... this is for a custom chip. > > ...Jim Thompson
Hmmm. RLC is a 'short' to GND How about make the circuitry so noisy that the RLC shorts EVERYTHING BUT the noise and the circuit just 'looks' like it oscillates? I mean narrowband noise is an oscillator output, right?
On Sat, 14 Mar 2015 10:07:50 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>Oscillator Proposal... > >Suppose I have a series RLC, one end grounded, the other end driven by >a chip, how might I make that into an oscillator? > >All wild ideas accepted... this is for a custom chip. > > ...Jim Thompson
How many wires will the chip have? 1 or 2? -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com