Favourite parts with off-label uses?

On Wednesday, April 8, 2020 at 8:31:51 AM UTC-4, Lasse Langwadt Christensen wrote:
> onsdag den 8. april 2020 kl. 10.31.41 UTC+2 skrev Clifford Heath:
> > On 8/4/20 1:51 pm, Clifford Heath wrote:
> > > On 8/4/20 12:39 pm, Gerhard Hoffmann wrote:
> > >> Am 08.04.20 um 03:05 schrieb Clifford Heath:
> > >> I have done that thing with the BFR93A many years ago
> > > 
> > > Oh, thanks, nice to know I'm on a right track. I basically just guessed 
> > > that the BFR93A should work, not that I saw it elsewhere.
> > > 
> > >> flat enough for tuning filters. Not good enough to measure
> > >> noise figure, both for amplitude and source impedance.
> > >> The breakdown voltage of the BFR93A was 5 or 6V IIRC.
> > >> I think it went to ~ 2 GHz.
> > > 
> > > That would be good enough for my first try!
> > > 
> > >> I used a CCS just like the charger
> > >> of my HP-35 :-)
> > > 
> > > I just thought I'd use a resistor, since I have a known supply voltage. 
> > > Not a good idea?
> > > 
> > >> Today I would not use a "Zener" source. If you have them, spend
> > >> 2 more ERAs and amplify the noise of a 50 Ohm resistor.
> > > 
> > > Well now it's interesting, but I have exactly the right amount of room 
> > > left on this proto-PCB for two more, and I have 20 ERA-3's.
> > > 
> > > It's on a grid-punched board with assorted top-side copper strips. I 
> > > used sticky-backed copper foil to make a ground plane on the back. It 
> > > doesn't seem such a bad way to prototype RF circuits, given that my 
> > > toner-transfer process is in recess (the new printer creates porous 
> > > blacks that don't etch well).
> > > 
> > >> Yes, they
> > >> have a noise figure of a few dB but you know it and it's flat.
> > > 
> > > Assuming the ERA-3 or the layout doesn't filter it, it should stay flat.
> > > 
> > >> 1K may produce more voltage noise,
> > >> but @ 50 Ohms you know that the ERAs will behave.
> > > 
> > > Well I could try 220R and just check it's not oscillating I guess. 
> > > Otherwise 50.
> > > 
> > >> The problem with noise filter measurements is that the bandwidth
> > >> of the noise is so large and if you want to see the stop band
> > >> you need lots of power. Thus, you will have large signal conditions
> > >> at the output of your noise generator. Getting closer to saturation
> > >> than 20 dB will damage the crest ratio / noise statistics.
> > > 
> > > Right. Not sure what that will do to the spectrum though?
> > 
> > 
> > Ok with 12V, 2.6mA through the BFR93A's b-e, it zeners at 5.8V.
> > 
> > Two stages of amplification is possibly too much - the noise is 
> > assymetrical around 0V, see this scope photo:
> > <https://www.dropbox.com/s/bmjnhm988160zjc/NoiseScope%20BFR93A%202.5mA%202xERA3.jpg?dl=0>
> > 
> 
> I seem to remember something about using two zeners and subtracting 
> them to get symmetric output

Yeah I've done that in the audio.  It helps some, but unless you match the 
zeners... Well symmetrical noise is over rated... no one cares much about 
low frequencies. 

George H. 

On Tuesday, April 7, 2020 at 9:25:45 AM UTC-4, George Herold wrote:
> On Monday, April 6, 2020 at 2:09:59 PM UTC-4, dagmarg...@yahoo.com wrote:
> > On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:
> > > Following up on blocher's sterling work,(*)
> > > 
> > > Many of us use parts off-label, often very successfully. A few examples:
> > > 
> > > SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. 
> > > 
> > > 74HC4352s make good flying-capacitor diff amp front ends.
> > > 
> > > TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster. 
> > > 
> > > Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit. 
> > > 
> > > Your faves?
> > > 
> > > Cheers 
> > > 
> > > Phil Hobbs 
> > > (*) who may be bulegoge's good twin, given the similarity of their emails ;)
> > 
> > o CMOS gates for power supplies, precision voltage switching,
> >   class-C r.f. power amps.
> > 
> > o Various semiconductor junctions as varicaps.
> > 
> > o I'm still searching for a way to use crappy ceramic caps as
> >   varactors.  Tuning a WWVB loop antenna might finally be that chance.
> 
> Hi James, I spent part of the weekend trying to think about 
> crappy ceramic caps as part of a parametric oscillator.  
> (After re-reading Pippard's "Physics of Vibration" 
> the oscillator seems like an easier first step.) 
> But I have no idea how to couple two different signals 
> into/ through the capacitor.  Well maybe a bridge.  
> 
> Do you have any clever ideas? 
> 
> George H.  

Sorry George, parametric amplifiers only momentarily grabbed my
attention ages ago (when I was trying to generate 1GHz from HCMOS).

I've always found that, except maybe at microwave frequencies that keep
getting higher and higher, active circuits won out.

Cheers,
James Arthur

On Wed, 8 Apr 2020 05:31:45 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>onsdag den 8. april 2020 kl. 10.31.41 UTC+2 skrev Clifford Heath:
>> On 8/4/20 1:51 pm, Clifford Heath wrote:
>> > On 8/4/20 12:39 pm, Gerhard Hoffmann wrote:
>> >> Am 08.04.20 um 03:05 schrieb Clifford Heath:
>> >> I have done that thing with the BFR93A many years ago
>> > 
>> > Oh, thanks, nice to know I'm on a right track. I basically just guessed 
>> > that the BFR93A should work, not that I saw it elsewhere.
>> > 
>> >> flat enough for tuning filters. Not good enough to measure
>> >> noise figure, both for amplitude and source impedance.
>> >> The breakdown voltage of the BFR93A was 5 or 6V IIRC.
>> >> I think it went to ~ 2 GHz.
>> > 
>> > That would be good enough for my first try!
>> > 
>> >> I used a CCS just like the charger
>> >> of my HP-35 :-)
>> > 
>> > I just thought I'd use a resistor, since I have a known supply voltage. 
>> > Not a good idea?
>> > 
>> >> Today I would not use a "Zener" source. If you have them, spend
>> >> 2 more ERAs and amplify the noise of a 50 Ohm resistor.
>> > 
>> > Well now it's interesting, but I have exactly the right amount of room 
>> > left on this proto-PCB for two more, and I have 20 ERA-3's.
>> > 
>> > It's on a grid-punched board with assorted top-side copper strips. I 
>> > used sticky-backed copper foil to make a ground plane on the back. It 
>> > doesn't seem such a bad way to prototype RF circuits, given that my 
>> > toner-transfer process is in recess (the new printer creates porous 
>> > blacks that don't etch well).
>> > 
>> >> Yes, they
>> >> have a noise figure of a few dB but you know it and it's flat.
>> > 
>> > Assuming the ERA-3 or the layout doesn't filter it, it should stay flat.
>> > 
>> >> 1K may produce more voltage noise,
>> >> but @ 50 Ohms you know that the ERAs will behave.
>> > 
>> > Well I could try 220R and just check it's not oscillating I guess. 
>> > Otherwise 50.
>> > 
>> >> The problem with noise filter measurements is that the bandwidth
>> >> of the noise is so large and if you want to see the stop band
>> >> you need lots of power. Thus, you will have large signal conditions
>> >> at the output of your noise generator. Getting closer to saturation
>> >> than 20 dB will damage the crest ratio / noise statistics.
>> > 
>> > Right. Not sure what that will do to the spectrum though?
>> 
>> 
>> Ok with 12V, 2.6mA through the BFR93A's b-e, it zeners at 5.8V.
>> 
>> Two stages of amplification is possibly too much - the noise is 
>> assymetrical around 0V, see this scope photo:
>> <https://www.dropbox.com/s/bmjnhm988160zjc/NoiseScope%20BFR93A%202.5mA%202xERA3.jpg?dl=0>
>> 
>
>I seem to remember something about using two zeners and subtracting 
>them to get symmetric output
>
>

That was also done with gas discharge noise tubes, essentially
thyratrons. There was also a trick of attaching a magnet to one tube
to make the noise symmetric. I haven't a clue why that would work.



-- 

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

  Claude Bernard
  

On Tue, 7 Apr 2020 06:25:39 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

>On Monday, April 6, 2020 at 2:09:59 PM UTC-4, dagmarg...@yahoo.com wrote:
>> On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:
>> > Following up on blocher's sterling work,(*)
>> > 
>> > Many of us use parts off-label, often very successfully. A few examples:
>> > 
>> > SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. 
>> > 
>> > 74HC4352s make good flying-capacitor diff amp front ends.
>> > 
>> > TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster. 
>> > 
>> > Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit. 
>> > 
>> > Your faves?
>> > 
>> > Cheers 
>> > 
>> > Phil Hobbs 
>> > (*) who may be bulegoge's good twin, given the similarity of their emails ;)
>> 
>> o CMOS gates for power supplies, precision voltage switching,
>>   class-C r.f. power amps.
>> 
>> o Various semiconductor junctions as varicaps.
>> 
>> o I'm still searching for a way to use crappy ceramic caps as
>>   varactors.  Tuning a WWVB loop antenna might finally be that chance.
>
>Hi James, I spent part of the weekend trying to think about 
>crappy ceramic caps as part of a parametric oscillator.  
>(After re-reading Pippard's "Physics of Vibration" 
>the oscillator seems like an easier first step.) 
>But I have no idea how to couple two different signals 
>into/ through the capacitor.  Well maybe a bridge.  
>
>Do you have any clever ideas? 
>
>George H.  
>
>> 
>> o LEDs as detectors.
>> 
>> Cheers,
>> James Arthur

I have thought about making an oscillator from a ceramic cap and
passives, but if it could be done probably someone would have done it.
It could certainly be done with a pump oscillator and some diodes and
stuff.

One use for nonlinear ceramic caps is to make high voltage shock
lines. Put a slow pulse into a shock line and it gets faster as it
propagates.





-- 

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

  Claude Bernard
  

20 ma LED current source chips make nice MMIC  current limiters in place of resistors.

20 ma Led current source chips plus optoisolators make nice protected interlock  inputs to 48 or  90VDC  depending on the chip, for a whopping 63 cents.

Steve 

On Wednesday, April 8, 2020 at 12:02:54 PM UTC-4, dagmarg...@yahoo.com wrote:
> On Tuesday, April 7, 2020 at 9:25:45 AM UTC-4, George Herold wrote:
> > On Monday, April 6, 2020 at 2:09:59 PM UTC-4, dagmarg...@yahoo.com wrote:
> > > On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:
> > > > Following up on blocher's sterling work,(*)
> > > > 
> > > > Many of us use parts off-label, often very successfully. A few examples:
> > > > 
> > > > SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. 
> > > > 
> > > > 74HC4352s make good flying-capacitor diff amp front ends.
> > > > 
> > > > TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster. 
> > > > 
> > > > Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit. 
> > > > 
> > > > Your faves?
> > > > 
> > > > Cheers 
> > > > 
> > > > Phil Hobbs 
> > > > (*) who may be bulegoge's good twin, given the similarity of their emails ;)
> > > 
> > > o CMOS gates for power supplies, precision voltage switching,
> > >   class-C r.f. power amps.
> > > 
> > > o Various semiconductor junctions as varicaps.
> > > 
> > > o I'm still searching for a way to use crappy ceramic caps as
> > >   varactors.  Tuning a WWVB loop antenna might finally be that chance.
> > 
> > Hi James, I spent part of the weekend trying to think about 
> > crappy ceramic caps as part of a parametric oscillator.  
> > (After re-reading Pippard's "Physics of Vibration" 
> > the oscillator seems like an easier first step.) 
> > But I have no idea how to couple two different signals 
> > into/ through the capacitor.  Well maybe a bridge.  
> > 
> > Do you have any clever ideas? 
> > 
> > George H.  
> 
> Sorry George, parametric amplifiers only momentarily grabbed my
> attention ages ago (when I was trying to generate 1GHz from HCMOS).
> 
> I've always found that, except maybe at microwave frequencies that keep
> getting higher and higher, active circuits won out.
No worries, I'm mostly interested for pedantic reasons.  
The only 'good' physics demo's of this are mechanical, AFAIK.
(oh and mag amps...) 

At some point I suffer from not understanding transformers well enough.
(like where the LF and HF corners are.)

George H. 
> 
> Cheers,
> James Arthur

On Wed, 8 Apr 2020 10:26:57 -0700 (PDT), sroberts6328@gmail.com wrote:

>20 ma LED current source chips make nice MMIC  current limiters in place of resistors.

Newer MMICs have internal current control loops, so can be biased from
a voltage source through an inductor. The control loops have various
weird low frequency effects. My new GHz o/e converter circuit will
only work with old-style MMICs.

>
>20 ma Led current source chips plus optoisolators make nice protected interlock  inputs to 48 or  90VDC  depending on the chip, for a whopping 63 cents.


The LED current limiters are cool, but most need a lot of voltage
drop.

There are some self-protecting SSRs that have low drop, basically pure
ohmic up to some hundreds of mA.


>
>Steve 
-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

On 9/4/20 12:34 am, George Herold wrote:
> On Wednesday, April 8, 2020 at 4:31:41 AM UTC-4, Clifford Heath wrote:
>> On 8/4/20 1:51 pm, Clifford Heath wrote:
>> Ok with 12V, 2.6mA through the BFR93A's b-e, it zeners at 5.8V.
>>
>> Two stages of amplification is possibly too much - the noise is
>> assymetrical around 0V, see this scope photo:
>> <https://www.dropbox.com/s/bmjnhm988160zjc/NoiseScope%20BFR93A%202.5mA%202xERA3.jpg?dl=0>
>>
>> I guess I need to reduce gain somewhat?
> Hi Cliff, I'm not at all a HF noise guy.
> (So listen to Gerhard and not me .:^)
> But the non-symmetry is typical.  You might want to look at the
> signal as a function of the bias current. That is your 'best' knob.

Oh, good to know, it didn't seem right that the ERA-3's could be 
producing this on overload. it makes sens that it's typical zener behaviour.

>> I haven't investigated the spectrum yet.
> How fast a 'scope do you have?  Have you tried triggering on the
> noise (pulses)  With a DSO you can average the pulses/ noise peaks
> and get a pseudo-spectrum... at least a guess at the max freq.

500MHz Tek 7904, with all the nice plug-in's :). No, I haven't tried 
triggering on it. But the noise looks almost the same regardless of the 
timebase, so that's a good sign.

But I also have a HackRF and I'm not ashamed to use it as a spectrum 
analyser.

Clifford Heath.

On 8/4/20 10:22 pm, Gerhard Hoffmann wrote:
> Am 08.04.20 um 05:51 schrieb Clifford Heath:
>> On 8/4/20 12:39 pm, Gerhard Hoffmann wrote:
>>> Getting closer to saturation
>>> than 20 dB will damage the crest ratio / noise statistics.
>> Right. Not sure what that will do to the spectrum though?
> 
> No idea. But a customer of mine had some problems with the
> autocorrelation of pseudo-noise for ranging purposes. The measured > S-curve did not look so triangle-like as it was supposed to be.

We'll see how the resistor noise looks. I'm just worried that much 
amplification will show the noise of the first ERA3, or power supply or 
ambient noise that I haven't filtered or screened out.

>> I'm using 0805 resistors but not series inductors, for now. Will that 
>> affect flatness (rather than just lose some gain)?
> 
> Pure resistance from high VCC is probably easier for the beginning.
> Use smaller R in series, it's a matter of C over the resistor vs. C from
> resistor to GND. You get predictability and spend VCC.

I could easily put a tiny wire loop inductor in series after the R, at 
risk of coupling to the next stage and singing. That should help at GHz.

> I had quite good success with home etching, it helps during the lock-down.

I had excellent success with toner transfer, handling 0.6mm pin-pitch 
parts easily, when I was using my ancient HP LJ6L. That finally died, 
and the replacement HP2055DN produces a porous checker-plate that's 
visible only under magnification. I haven't worked out how to stop it 
doing that, but the etchant gets through the tiny gaps, even if I use 
the toner transfer foil. Perhaps I'll have another go at it, I've only 
tried etching once (printing many times, but only one seemed good enough 
to etch.

I leave the back side as solid copper, just fitting jumper wires if I 
need a trace. If I can't route mostly single-sided, I don't make it myself.

> This here is from the same double-sided Eurocard (100 * 160 mm); the
> foil has been made with a Kyocera color laser on Bungard pre-sensitized
> material. I can etch what I can print. The A3 OKI color laser I used to
> have previously was clearly better, but the machine was a royal pain.



> The bottom side is GND and unetched. No ado with alignment.

On Wednesday, April 8, 2020 at 7:20:56 PM UTC-4, Clifford Heath wrote:
> On 8/4/20 10:22 pm, Gerhard Hoffmann wrote:
> > Am 08.04.20 um 05:51 schrieb Clifford Heath:
> >> On 8/4/20 12:39 pm, Gerhard Hoffmann wrote:
> >>> Getting closer to saturation
> >>> than 20 dB will damage the crest ratio / noise statistics.
> >> Right. Not sure what that will do to the spectrum though?
> > 
> > No idea. But a customer of mine had some problems with the
> > autocorrelation of pseudo-noise for ranging purposes. The measured > S-curve did not look so triangle-like as it was supposed to be.
> 
> We'll see how the resistor noise looks. I'm just worried that much 
> amplification will show the noise of the first ERA3, or power supply or 
> ambient noise that I haven't filtered or screened out.
> 
> >> I'm using 0805 resistors but not series inductors, for now. Will that 
> >> affect flatness (rather than just lose some gain)?
> > 
> > Pure resistance from high VCC is probably easier for the beginning.
> > Use smaller R in series, it's a matter of C over the resistor vs. C from
> > resistor to GND. You get predictability and spend VCC.
> 
> I could easily put a tiny wire loop inductor in series after the R, at 
> risk of coupling to the next stage and singing. That should help at GHz.
> 
> > I had quite good success with home etching, it helps during the lock-down.
> 
> I had excellent success with toner transfer, handling 0.6mm pin-pitch 
> parts easily, when I was using my ancient HP LJ6L. That finally died, 
> and the replacement HP2055DN produces a porous checker-plate that's 
> visible only under magnification. I haven't worked out how to stop it 
> doing that, but the etchant gets through the tiny gaps, even if I use 
> the toner transfer foil. Perhaps I'll have another go at it, I've only 
> tried etching once (printing many times, but only one seemed good enough 
> to etch.

I haven't been able to get toner transfer working since I changed
toner carts. But I've dabbled with two promising variations.

1) If you lacquer-coat the PCB *then* transfer the toner, the
lacquer fills in the toner's pores.  The lacquer itself, meanwhile,
can be easily removed with alcohol, but the toner's pores seem to
stay filled.

The toner image is printed on the paper you peel off the back of
adhesive labels, or in my case, backing peeled off adhesive
shelf-liner paper from the one-dollar store.

2) A variation of the above is to spray the lacquer, then transfer
the toner almost immediately, before the lacquer dries. The lacquer
itself grabs the toner.
https://www.youtube.com/watch?v=0dpCi9kgpuw

3) A third method is to zap the toner with acetone/alcohol mix to
make the toner tacky, then stick it to the board. That always
smears the traces when I try it. "Cold Toner Transfer"
e.g. https://www.youtube.com/watch?v=cVhSCEPINpM

Cheers,
James Arthur