On Monday, March 6, 2023 at 4:51:54 AM UTC+11, Cursitor Doom wrote:> Gentlemen, > > Over the years, I have found that there is one circuit fragment above > all others that I go back to repeatedly, and that is the PWM > controller in all its guises. I have made more of these than any other > electronic sub-circuit over the last 50 years and they come in handy > for all manner of different applications. > I'm just curious to know what others here find themselves going back > to repeatedly over the years and would welcome responses from sed > contributors north of the Tropic of Capricorn in this regard.Only half-wits get fixated on particular solutions. John Fields thought that the NE555 was the solution to every problem. If you are such a half-wit, you end up avoiding problems that can't be solved with only tool you have in your tool box. Real-world engineers don't have that luxury. -- Bill Sloman, Sydney
Go To Circuits
Started by ●March 5, 2023
Reply by ●March 6, 20232023-03-06
Reply by ●March 6, 20232023-03-06
On 2023-03-06 02:23, Jan Panteltje wrote:> On a sunny day (Sun, 5 Mar 2023 13:33:22 -0500) it happened Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote in > <eeff52ba-cedf-6aed-3b21-0a84597f78e4@electrooptical.net>: > >> On 2023-03-05 12:51, Cursitor Doom wrote: >>> Gentlemen, >>> >>> Over the years, I have found that there is one circuit fragment above >>> all others that I go back to repeatedly, and that is the PWM >>> controller in all its guises. I have made more of these than any other >>> electronic sub-circuit over the last 50 years and they come in handy >>> for all manner of different applications. >>> I'm just curious to know what others here find themselves going back >>> to repeatedly over the years and would welcome responses from sed >>> contributors north of the Tropic of Capricorn in this regard. >>> >>> Cheers, >>> >>> CD. >>> >> >> Bootstraps, superhets of one sort or another, noise cancellers, cap >> multipliers, AC-coupled feedback loops, and a cast of thousands. ;) > > Phil did you ever look into the RTL-SDR world? > https://www.rtl-sdr.com/about-rtl-sdr/ > https://www.onelectrontech.com/rtl-sdr-v3-teardown-and-analysis/ > Those sticks (and the chips) are available and can replace much of your RF stuff. > I have 4 in use now..... > one as spectrum analyzer + radio receiver (stereo FM) + radar detector + GPS reception + ham radio (AM FM SSB) plus any other RF. > one to receive air traffic, one to receive ship traffic > and one to receive data from my outside weather station. > > So first RF thing I turn to. > Of course I have a real Tecsun PL600 radio too :-) > Plus ...Sure, they have their place--I talk about them in my third edition. Main issue is crappy dynamic range due to 8-bit digitizers. Second biggest one is crappy phase noise, which they have in common with all SDR-type systems.> And can replace tons of boat anchors.For some purposes, mostly very undemanding ones. My HP 8566B has 30-dB better close-in phase noise than any SDR-style analyzer I've seen.> https://panteltje.nl/panteltje/xpsa/index.html > old version software, new one has many more buttons and FM stereo and even runs on a Raspberry Pi > or your x86 leptop. > Lots of open source software for it on the internet. >Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●March 6, 20232023-03-06
On 2023-03-06 03:02, Gerhard Hoffmann wrote:> Am 05.03.23 um 19:33 schrieb Phil Hobbs: >> On 2023-03-05 12:51, Cursitor Doom wrote: >>> Gentlemen, >>> >>> Over the years, I have found that there is one circuit fragment above >>> all others that I go back to repeatedly, and that is the PWM >>> controller in all its guises. I have made more of these than any other >>> electronic sub-circuit over the last 50 years and they come in handy >>> for all manner of different applications. >>> I'm just curious to know what others here find themselves going back >>> to repeatedly over the years and would welcome responses from sed >>> contributors north of the Tropic of Capricorn in this regard. >>> >>> Cheers, >>> >>> CD. >>> >> >> Bootstraps, superhets of one sort or another, noise cancellers, cap >> multipliers, AC-coupled feedback loops, and a cast of thousands. ;) > > Hi, > > What are the Go To Laser drivers when the first 5 requirements > are stability and low noise? Just DC, no modulation.A PNP simulated inductor with a very long tail and a low noise op amp wrapped round it. The key is to drop lots of voltage in the emitter resistor and bypass the base to the positive supply rather than to ground. Two poles work better than one. With 5V drop across the resistor, you can get down to 20 dB below full shot noise, which has interesting consequences with some lasers.> Libbrecht-Hall or current_mirror++ ? > The Howland CCS probably does not need to apply.Cheers Phil -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●March 6, 20232023-03-06
On Monday, March 6, 2023 at 7:39:45 AM UTC-8, Phil Hobbs wrote:> On 2023-03-06 03:02, Gerhard Hoffmann wrote:> > What are the Go To Laser drivers when the first 5 requirements > > are stability and low noise? Just DC, no modulation.> A PNP simulated inductor with a very long tail and a low noise op amp > wrapped round it. The key is to drop lots of voltage in the emitter > resistor and bypass the base to the positive supply rather than to > ground. Two poles work better than one. With 5V drop across the > resistor, you can get down to 20 dB below full shot noise, which has > interesting consequences with some lasers.Good plan; the transistor has more bandwidth than the op amp. Two questions: would a MOSFET give equivalent performance to a PNP, and is a small inductor in series with the emitter resistor any benefit (I'm thinking of Rbb/Miller-effect cutoff of the transistor base bypass effectiveness).
Reply by ●March 6, 20232023-03-06
On 2023-03-06 13:40, whit3rd wrote:> On Monday, March 6, 2023 at 7:39:45 AM UTC-8, Phil Hobbs wrote: >> On 2023-03-06 03:02, Gerhard Hoffmann wrote: > >>> What are the Go To Laser drivers when the first 5 requirements >>> are stability and low noise? Just DC, no modulation. > >> A PNP simulated inductor with a very long tail and a low noise op amp >> wrapped round it. The key is to drop lots of voltage in the emitter >> resistor and bypass the base to the positive supply rather than to >> ground. Two poles work better than one. With 5V drop across the >> resistor, you can get down to 20 dB below full shot noise, which has >> interesting consequences with some lasers. > > Good plan; the transistor has more bandwidth than the op amp. > > Two questions: would a MOSFET give equivalent performance to a PNP, > and is a small inductor in series with the emitter resistor any benefit > (I'm thinking of Rbb/Miller-effect cutoff of the transistor base bypass effectiveness). >"No" to #1, and "possibly but generally not" to #2. MOSFETs are noisy and have crappy g_M for the same current. The way I build laser drivers, the emitter resistor is pretty large, so as to get below the shot noise on the output. The total noise goes down by 3 dB when the emitter resistor drops 2kT/e (51 mV @ 300K), and I try to run it at least a few volts. Thus in order to make a difference over a wide bandwidth, the inductor it would have to be pretty massive. On the other hand, once its effect dominated, it would reduce the shot noise characteristic further, without needing extra headroom. Being (ideally) noiseless, it would also win linearly rather than as the square root. Keeping the transistor stable despite a low-Z base bypass might take a bit of care as well. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●March 7, 20232023-03-07
On a sunny day (Mon, 6 Mar 2023 10:27:09 -0500) it happened Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in <2c5b0e6f-a3fc-03b2-4e9b-e71ffb5f33bf@electrooptical.net>:>On 2023-03-06 02:23, Jan Panteltje wrote: >> On a sunny day (Sun, 5 Mar 2023 13:33:22 -0500) it happened Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote in >> <eeff52ba-cedf-6aed-3b21-0a84597f78e4@electrooptical.net>: >> >>> On 2023-03-05 12:51, Cursitor Doom wrote: >>>> Gentlemen, >>>> >>>> Over the years, I have found that there is one circuit fragment above >>>> all others that I go back to repeatedly, and that is the PWM >>>> controller in all its guises. I have made more of these than any other >>>> electronic sub-circuit over the last 50 years and they come in handy >>>> for all manner of different applications. >>>> I'm just curious to know what others here find themselves going back >>>> to repeatedly over the years and would welcome responses from sed >>>> contributors north of the Tropic of Capricorn in this regard. >>>> >>>> Cheers, >>>> >>>> CD. >>>> >>> >>> Bootstraps, superhets of one sort or another, noise cancellers, cap >>> multipliers, AC-coupled feedback loops, and a cast of thousands. ;) >> >> Phil did you ever look into the RTL-SDR world? >> https://www.rtl-sdr.com/about-rtl-sdr/ >> https://www.onelectrontech.com/rtl-sdr-v3-teardown-and-analysis/ >> Those sticks (and the chips) are available and can replace much of your RF stuff. >> I have 4 in use now..... >> one as spectrum analyzer + radio receiver (stereo FM) + radar detector + GPS reception + ham radio (AM FM SSB) plus any other >> RF. >> one to receive air traffic, one to receive ship traffic >> and one to receive data from my outside weather station. >> >> So first RF thing I turn to. >> Of course I have a real Tecsun PL600 radio too :-) >> Plus ... > >Sure, they have their place--I talk about them in my third edition. > >Main issue is crappy dynamic range due to 8-bit digitizers. Second >biggest one is crappy phase noise, which they have in common with all >SDR-type systems. > >> And can replace tons of boat anchors. > >For some purposes, mostly very undemanding ones. My HP 8566B has 30-dB >better close-in phase noise than any SDR-style analyzer I've seen.OK, sure, 8 bits, but it never hindered me so far.. This is a nice article about GPS receiving with the RTL-SDR: http://michelebavaro.blogspot.com/2012/04/spring-news-in-gnss-and-sdr-domain.html Of coure I had to try it, scroll down to 'panteltje' in that link note the links to my site are now on panteltje.nl: https://panteltje.nl/pub/run_50_outside_2728000.gif https://panteltje.nl/pub/GPS_antenna_T_power_section_IMG_3790.GIF Bit of mathlab (I used octave)... Thing is very sensitive... The big square thing is the active GPS antenna, the small square thing the RTL-SDR [1] So with a good low noise signal much is possible. When and were is your third edition coming out? [1] no idea where I left it, so I have 5 .. hopefully I did not throw it away when moving house... :-) The latest ones are from ebay and all 1 ppm. old one with USB connector burned : https://panteltje.nl/pub/RTL2832_E4000_tuner_PCB_USB_connector_burned_holes_IMG_4671.JPG put in a new box: https://www.panteltje.nl/pub/E4000_tuner_in_better_box_with_SMA_IMG_4676.JPG It does draw some power, the new ones get hot (xtal is temperature controlled). Latest ones go down to 500 kHz, had build in bias circuit: https://www.ebay.com/itm/272411458376 have not tried that one, seller is OK, have 2 from them.>> https://panteltje.nl/panteltje/xpsa/index.html >> old version software, new one has many more buttons and FM stereo and even runs on a Raspberry Pi >> or your x86 leptop. >> Lots of open source software for it on the internet.
Reply by ●March 8, 20232023-03-08
Am 06.03.23 um 16:39 schrieb Phil Hobbs:> On 2023-03-06 03:02, Gerhard Hoffmann wrote:>> What are the Go To Laser drivers when the first 5 requirements >> are stability and low noise? Just DC, no modulation. > > A PNP simulated inductor with a very long tail and a low noise op amp > wrapped round it.I suppose PNP b/c of the slightly better voltage noise than a similar NPN, and the inductor is just the 6 dB/oct drop, or is there more to it?> The key is to drop lots of voltage in the emitter > resistor and bypass the base to the positive supply rather than to > ground. Two poles work better than one. With 5V drop across the > resistor, you can get down to 20 dB below full shot noise, which has > interesting consequences with some lasers.Now I'm curious. What would these consequences be? Cheers Gerhard
Reply by ●March 8, 20232023-03-08
On 2023-03-08 13:30, Gerhard Hoffmann wrote:> Am 06.03.23 um 16:39 schrieb Phil Hobbs: >> On 2023-03-06 03:02, Gerhard Hoffmann wrote: > >>> What are the Go To Laser drivers when the first 5 requirements >>> are stability and low noise? Just DC, no modulation. >> >> A PNP simulated inductor with a very long tail and a low noise op amp >> wrapped round it. > > I suppose PNP b/c of the slightly better voltage noise than a > similar NPN, and the inductor is just the 6 dB/oct drop, or is there > more to it?Common-cathode laser. The 'simulated inductor' thing is just a cap multiplier with the base bypassed to the far end of the emitter resistor rather than to ground. Like this: V+ 0--*--RRRR--* *------------------* | \ / | | V / --- | ------- \ / ~~ > | C C | V ~~ > *- C C------*-----RRRR---0 Vctl --- C C | GGG with maybe another pole (also bypassed to V+) for good measure, and a nice quiet op amp looking at the same resistor, doing the DC regulation.>> The key is to drop lots of voltage in the emitter resistor and bypass >> the base to the positive supply rather than to ground. Two poles work >> better than one. With 5V drop across the resistor, you can get down >> to 20 dB below full shot noise, which has interesting consequences >> with some lasers. > > Now I'm curious. What would these consequences be?Amplitude squeezing, sometimes. Thirty-odd years ago, all sorts of quantum optics folk were working on "squeezed states", in which the Heisenberg uncertainty product <delta A><delta phi> was modified to give less <delta A> and more <delta phi>. It was all Ti:sapphire lasers and optical parametric oscillators and four-wave mixing and stuff--tables full of expensive parts on expensive mounts, conferences with big banquets, yada yada, all to get about a decibel worth. Then these Japanese guys (whose paper I can't seem to locate) took a LN2-cooled diode laser, biased it with a stack of batteries and a big resistor, and got 3 dB, because the bias current was way sub-Poissonian and that constrained the pumping. They had the world record for some years, iirc. (I love things like that--doing something amazing with almost zero apparatus.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●March 8, 20232023-03-08
On 2023-03-08 14:06, Phil Hobbs wrote:> On 2023-03-08 13:30, Gerhard Hoffmann wrote: >> Am 06.03.23 um 16:39 schrieb Phil Hobbs: >>> On 2023-03-06 03:02, Gerhard Hoffmann wrote: >> >>>> What are the Go To Laser drivers when the first 5 requirements >>>> are stability and low noise? Just DC, no modulation. >>> >>> A PNP simulated inductor with a very long tail and a low noise op amp >>> wrapped round it. >> >> I suppose PNP b/c of the slightly better voltage noise than a >> similar NPN, and the inductor is just the 6 dB/oct drop, or is there >> more to it? > > Common-cathode laser. The 'simulated inductor' thing is just a cap > multiplier with the base bypassed to the far end of the emitter resistor > rather than to ground. Like this: > > V+ > 0--*--RRRR--* *------------------* > | \ / | > | V / --- > | ------- \ / ~~ > > | C C | V ~~ > > *- C C------*-----RRRR---0 Vctl --- > C C | > GGG > > with maybe another pole (also bypassed to V+) for good measure, and a > nice quiet op amp looking at the same resistor, doing the DC regulation. > >>> The key is to drop lots of voltage in the emitter resistor and >>> bypass the base to the positive supply rather than to ground. Two >>> poles work better than one. With 5V drop across the resistor, you >>> can get down to 20 dB below full shot noise, which has interesting >>> consequences with some lasers. >> >> Now I'm curious. What would these consequences be? > > Amplitude squeezing, sometimes. Thirty-odd years ago, all sorts of > quantum optics folk were working on "squeezed states", in which the > Heisenberg uncertainty product <delta A><delta phi> was modified to give > less <delta A> and more <delta phi>. > > It was all Ti:sapphire lasers and optical parametric oscillators and > four-wave mixing and stuff--tables full of expensive parts on expensive > mounts, conferences with big banquets, yada yada, all to get about a > decibel worth. > > Then these Japanese guys (whose paper I can't seem to locate) took a > LN2-cooled diode laser, biased it with a stack of batteries and a big > resistor, and got 3 dB, because the bias current was way sub-Poissonian > and that constrained the pumping.Machida and Yamamoto, it was. One of their early pubs is <https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.60.792>> > They had the world record for some years, iirc. (I love things like > that--doing something amazing with almost zero apparatus.)Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
