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bipolar aluminum caps

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  bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 07:01 -0700
    Re: bipolar aluminum caps George Herold <gherold@teachspin.com> - 2016-10-13 07:11 -0700
      Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-15 00:38 -0800
    Re: bipolar aluminum caps tabbypurr@gmail.com - 2016-10-13 07:34 -0700
      Re: bipolar aluminum caps Reinhardt Behm <rbehm@hushmail.com> - 2016-10-13 22:58 +0800
      Re: bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 08:44 -0700
        Re: bipolar aluminum caps tabbypurr@gmail.com - 2016-10-13 08:59 -0700
          Re: bipolar aluminum caps George Herold <gherold@teachspin.com> - 2016-10-13 09:14 -0700
            Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 03:40 -0500
              Re: bipolar aluminum caps Syd Rumpo <usenet@nononono.co.uk> - 2016-10-14 09:52 +0100
                Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 03:59 -0500
                  Re: bipolar aluminum caps Syd Rumpo <usenet@nononono.co.uk> - 2016-10-14 11:01 +0100
                    Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 21:48 -0500
                Re: bipolar aluminum caps tabbypurr@gmail.com - 2016-10-14 02:18 -0700
        Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-15 00:45 -0800
          Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-15 11:06 -0400
            Re: bipolar aluminum caps tabbypurr@gmail.com - 2016-10-15 08:23 -0700
              Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-15 19:39 -0400
          Re: bipolar aluminum caps Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2016-10-18 21:23 -0400
      Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-15 00:42 -0800
        Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-15 11:07 -0400
          Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-17 09:28 -0800
            Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-17 19:52 -0400
              Re: bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-17 17:29 -0700
              Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-19 13:06 -0800
    Re: bipolar aluminum caps Joerg <news@analogconsultants.com> - 2016-10-13 09:14 -0700
    Re: bipolar aluminum caps Frank Miles <fpm@u.washington.edu> - 2016-10-13 17:15 +0000
      Re: bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 11:42 -0700
        Re: bipolar aluminum caps Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2016-10-13 14:52 -0400
          Re: bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 11:56 -0700
          Re: bipolar aluminum caps "David Eather" <eather@tpg.com.au> - 2016-10-15 14:53 +1000
      Re: bipolar aluminum caps "David Eather" <eather@tpg.com.au> - 2016-10-15 14:52 +1000
    Re: bipolar aluminum caps Tim Wescott <tim@seemywebsite.really> - 2016-10-13 19:41 -0500
      Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 03:43 -0500
        Re: bipolar aluminum caps Tim Wescott <seemywebsite@myfooter.really> - 2016-10-14 12:19 -0500
          Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 22:18 -0500
    Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-13 20:57 -0400
      Re: bipolar aluminum caps John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 18:05 -0700
        Re: bipolar aluminum caps krw <krw@nowhere.com> - 2016-10-13 21:39 -0400
          Re: bipolar aluminum caps "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-14 03:44 -0500
            Re: bipolar aluminum caps whit3rd <whit3rd@gmail.com> - 2016-10-14 12:22 -0700
    Re: bipolar aluminum caps whit3rd <whit3rd@gmail.com> - 2016-10-13 18:01 -0700
    Re: bipolar aluminum caps alpibucky <alpibucky@mail.be> - 2016-10-14 22:23 +0200
    Re: bipolar aluminum caps Robert Baer <robertbaer@localnet.com> - 2016-10-15 00:35 -0800
      Re: bipolar aluminum caps Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2016-10-18 21:22 -0400

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#431301

On Sat, 15 Oct 2016 00:42:08 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

>tabbypurr@gmail.com wrote:
>> On Thursday, 13 October 2016 15:02:02 UTC+1, John Larkin  wrote:
>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>> rated voltage.
>>>
>>> Are bipolar aluminum caps reliable?
>>>
>>> I would think that polymer aluminum caps would make good nonpolarized
>>> things, but there don't seem to be any.
>>
>> Tants make good bipolars ;)
>>
>>
>> NT
>   A monopolar tantalum is shit at inverse voltage, and you take the 
>risk of explosion. Even if you do the standard of derating by an order 
>of magnitude.

Your "standard de-rating" is *way* to high.  

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#431534

krw wrote:
> On Sat, 15 Oct 2016 00:42:08 -0800, Robert Baer
> <robertbaer@localnet.com>  wrote:
>
>> tabbypurr@gmail.com wrote:
>>> On Thursday, 13 October 2016 15:02:02 UTC+1, John Larkin  wrote:
>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>> rated voltage.
>>>>
>>>> Are bipolar aluminum caps reliable?
>>>>
>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>> things, but there don't seem to be any.
>>>
>>> Tants make good bipolars ;)
>>>
>>>
>>> NT
>>    A monopolar tantalum is shit at inverse voltage, and you take the
>> risk of explosion. Even if you do the standard of derating by an order
>> of magnitude.
>
> Your "standard de-rating" is *way* to high.
   Do not complain to me when a problem happens...

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#431579

On Mon, 17 Oct 2016 09:28:38 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

>krw wrote:
>> On Sat, 15 Oct 2016 00:42:08 -0800, Robert Baer
>> <robertbaer@localnet.com>  wrote:
>>
>>> tabbypurr@gmail.com wrote:
>>>> On Thursday, 13 October 2016 15:02:02 UTC+1, John Larkin  wrote:
>>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>>> rated voltage.
>>>>>
>>>>> Are bipolar aluminum caps reliable?
>>>>>
>>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>>> things, but there don't seem to be any.
>>>>
>>>> Tants make good bipolars ;)
>>>>
>>>>
>>>> NT
>>>    A monopolar tantalum is shit at inverse voltage, and you take the
>>> risk of explosion. Even if you do the standard of derating by an order
>>> of magnitude.
>>
>> Your "standard de-rating" is *way* to high.
>   Do not complain to me when a problem happens...

Other way around.  *You* will have trouble keeping the electrolytic
formed.  I haven't used tantalums in years, though (too expensive).

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#431588

On Mon, 17 Oct 2016 19:52:31 -0400, krw <krw@nowhere.com> wrote:

>On Mon, 17 Oct 2016 09:28:38 -0800, Robert Baer
><robertbaer@localnet.com> wrote:
>
>>krw wrote:
>>> On Sat, 15 Oct 2016 00:42:08 -0800, Robert Baer
>>> <robertbaer@localnet.com>  wrote:
>>>
>>>> tabbypurr@gmail.com wrote:
>>>>> On Thursday, 13 October 2016 15:02:02 UTC+1, John Larkin  wrote:
>>>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>>>> rated voltage.
>>>>>>
>>>>>> Are bipolar aluminum caps reliable?
>>>>>>
>>>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>>>> things, but there don't seem to be any.
>>>>>
>>>>> Tants make good bipolars ;)
>>>>>
>>>>>
>>>>> NT
>>>>    A monopolar tantalum is shit at inverse voltage, and you take the
>>>> risk of explosion. Even if you do the standard of derating by an order
>>>> of magnitude.
>>>
>>> Your "standard de-rating" is *way* to high.
>>   Do not complain to me when a problem happens...
>
>Other way around.  *You* will have trouble keeping the electrolytic
>formed.  I haven't used tantalums in years, though (too expensive).

We use tons of surface-mount tantalums, in the 5 to 10 cents each
range. I derate them 3:1 if they are on regulator outputs; their ESR
behavior suits many regulators just right. They have practically no
inductance.

I don't use tants on power input rails where lots of surge current is
possible.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#431863

krw wrote:
> On Mon, 17 Oct 2016 09:28:38 -0800, Robert Baer
> <robertbaer@localnet.com>  wrote:
>
>> krw wrote:
>>> On Sat, 15 Oct 2016 00:42:08 -0800, Robert Baer
>>> <robertbaer@localnet.com>   wrote:
>>>
>>>> tabbypurr@gmail.com wrote:
>>>>> On Thursday, 13 October 2016 15:02:02 UTC+1, John Larkin  wrote:
>>>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>>>> rated voltage.
>>>>>>
>>>>>> Are bipolar aluminum caps reliable?
>>>>>>
>>>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>>>> things, but there don't seem to be any.
>>>>>
>>>>> Tants make good bipolars ;)
>>>>>
>>>>>
>>>>> NT
>>>>     A monopolar tantalum is shit at inverse voltage, and you take the
>>>> risk of explosion. Even if you do the standard of derating by an order
>>>> of magnitude.
>>>
>>> Your "standard de-rating" is *way* to high.
>>    Do not complain to me when a problem happens...
>
> Other way around.  *You* will have trouble keeping the electrolytic
> formed.  I haven't used tantalums in years, though (too expensive).
   Well, i have had a number of the old style wet electrolytics that 
were working at the time for about 10 years and most were only low in 
capacitance.
   All they needed was some liquid rejuvenation and forming to continue 
operation to specs for 5 years.
   The vents on top were there to allow this.

   Also,the old Tek scopes (10 years or so) some of which had been 
standing in the weather (LA area) were re-formed by easy and simple 
well-established techniques.

   Apparently you need more education.

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#431120

On 2016-10-13 07:01, John Larkin wrote:
>
>
> High-K ceramic caps are awful. They lose 90% of their capacitance at
> rated voltage.
>

Talk to Murata. IME they have among the best "figure of merit" caps when 
it comes to high relative dieletrci constant and capacitance loss over 
applies voltage. Their TechHelp folks are quite knowledgeable.


> Are bipolar aluminum caps reliable?
>

I don't trust electrolytics much and only use them if I really have to. 
Especially on hi-rel design.


> I would think that polymer aluminum caps would make good nonpolarized
> things, but there don't seem to be any.
>

Passive power filters for audio were a major market but with the advent 
of active speakers that segment has shriveled up. Many people don't even 
have a stereo with huge speakers anymore. Other than some diehard boomers.

-- 
Regards, Joerg

http://www.analogconsultants.com/

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#431129

On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:

> High-K ceramic caps are awful. They lose 90% of their capacitance at
> rated voltage.
> 
> Are bipolar aluminum caps reliable?
> 
> I would think that polymer aluminum caps would make good nonpolarized
> things, but there don't seem to be any.

My dim recollection is that a bipolar electrolytic is equivalent to
back-to-back polarized electrolytics.  That is, you get twice the ESR & 
ESL, and some weirdness around 0-volts.  I'd be nervous if the current
was appreciable.  However they've been used for many years in lots of
applications, mostly in moderate-level coupling applications where
distortion wasn't an issue.  Probably as reliable as a standard 
electrolytic.

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#431137

On Thu, 13 Oct 2016 17:15:33 -0000 (UTC), Frank Miles
<fpm@u.washington.edu> wrote:

>On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:
>
>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>> rated voltage.
>> 
>> Are bipolar aluminum caps reliable?
>> 
>> I would think that polymer aluminum caps would make good nonpolarized
>> things, but there don't seem to be any.
>
>My dim recollection is that a bipolar electrolytic is equivalent to
>back-to-back polarized electrolytics.  That is, you get twice the ESR & 
>ESL, and some weirdness around 0-volts.  I'd be nervous if the current
>was appreciable.  However they've been used for many years in lots of
>applications, mostly in moderate-level coupling applications where
>distortion wasn't an issue.  Probably as reliable as a standard 
>electrolytic.

I guess I could do something like this...


---------+   << needs to go +15 to -6
         |
         |
         |
        ___ +
        ___     47u 25V

         |
         +-----R---- -6V
         |
        ___
        ___     220u 6V
         |  +
         |
         |
         |
         |
         |
        gnd


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#431139

On 10/13/2016 02:42 PM, John Larkin wrote:
> On Thu, 13 Oct 2016 17:15:33 -0000 (UTC), Frank Miles
> <fpm@u.washington.edu> wrote:
> 
>> On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:
>>
>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>> rated voltage.
>>>
>>> Are bipolar aluminum caps reliable?
>>>
>>> I would think that polymer aluminum caps would make good nonpolarized
>>> things, but there don't seem to be any.
>>
>> My dim recollection is that a bipolar electrolytic is equivalent to
>> back-to-back polarized electrolytics.  That is, you get twice the ESR & 
>> ESL, and some weirdness around 0-volts.  I'd be nervous if the current
>> was appreciable.  However they've been used for many years in lots of
>> applications, mostly in moderate-level coupling applications where
>> distortion wasn't an issue.  Probably as reliable as a standard 
>> electrolytic.
> 
> I guess I could do something like this...
> 
> 
> ---------+   << needs to go +15 to -6
>          |
>          |
>          |
>         ___ +
>         ___     47u 25V
> 
>          |
>          +-----R---- -6V
>          |
>         ___
>         ___     220u 6V
>          |  +
>          |
>          |
>          |
>          |
>          |
>         gnd
> 
> 

I'd still add a diode across each cap.  That -20/+80% spec range could
make a bit of a mess otherwise.

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

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#431140

On Thu, 13 Oct 2016 14:52:40 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 10/13/2016 02:42 PM, John Larkin wrote:
>> On Thu, 13 Oct 2016 17:15:33 -0000 (UTC), Frank Miles
>> <fpm@u.washington.edu> wrote:
>> 
>>> On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:
>>>
>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>> rated voltage.
>>>>
>>>> Are bipolar aluminum caps reliable?
>>>>
>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>> things, but there don't seem to be any.
>>>
>>> My dim recollection is that a bipolar electrolytic is equivalent to
>>> back-to-back polarized electrolytics.  That is, you get twice the ESR & 
>>> ESL, and some weirdness around 0-volts.  I'd be nervous if the current
>>> was appreciable.  However they've been used for many years in lots of
>>> applications, mostly in moderate-level coupling applications where
>>> distortion wasn't an issue.  Probably as reliable as a standard 
>>> electrolytic.
>> 
>> I guess I could do something like this...
>> 
>> 
>> ---------+   << needs to go +15 to -6
>>          |
>>          |
>>          |
>>         ___ +
>>         ___     47u 25V
>> 
>>          |
>>          +-----R---- -6V
>>          |
>>         ___
>>         ___     220u 6V
>>          |  +
>>          |
>>          |
>>          |
>>          |
>>          |
>>         gnd
>> 
>> 
>
>I'd still add a diode across each cap.  That -20/+80% spec range could
>make a bit of a mess otherwise.
>
>Cheers
>
>Phil Hobbs

If R=0, the top cap is just low-sided to the -6 supply and the bottom
cap bypasses that, which I should do anyhow.

Do people still say "duh" ?




-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#431269

On Fri, 14 Oct 2016 04:52:40 +1000, Phil Hobbs  
<pcdhSpamMeSenseless@electrooptical.net> wrote:

> On 10/13/2016 02:42 PM, John Larkin wrote:
>> On Thu, 13 Oct 2016 17:15:33 -0000 (UTC), Frank Miles
>> <fpm@u.washington.edu> wrote:
>>
>>> On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:
>>>
>>>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>> rated voltage.
>>>>
>>>> Are bipolar aluminum caps reliable?
>>>>
>>>> I would think that polymer aluminum caps would make good nonpolarized
>>>> things, but there don't seem to be any.
>>>
>>> My dim recollection is that a bipolar electrolytic is equivalent to
>>> back-to-back polarized electrolytics.  That is, you get twice the ESR &
>>> ESL, and some weirdness around 0-volts.  I'd be nervous if the current
>>> was appreciable.  However they've been used for many years in lots of
>>> applications, mostly in moderate-level coupling applications where
>>> distortion wasn't an issue.  Probably as reliable as a standard
>>> electrolytic.
>>
>> I guess I could do something like this...
>>
>>
>> ---------+   << needs to go +15 to -6
>>          |
>>          |
>>          |
>>         ___ +
>>         ___     47u 25V
>>
>>          |
>>          +-----R---- -6V
>>          |
>>         ___
>>         ___     220u 6V
>>          |  +
>>          |
>>          |
>>          |
>>          |
>>          |
>>         gnd
>>
>>
>
> I'd still add a diode across each cap.  That -20/+80% spec range could
> make a bit of a mess otherwise.
>
> Cheers
>
> Phil Hobbs
>

and there Phil has it 24hrs earlier

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#431268

On Fri, 14 Oct 2016 03:15:33 +1000, Frank Miles <fpm@u.washington.edu>  
wrote:

> On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:
>
>> High-K ceramic caps are awful. They lose 90% of their capacitance at
>> rated voltage.
>>
>> Are bipolar aluminum caps reliable?
>>
>> I would think that polymer aluminum caps would make good nonpolarized
>> things, but there don't seem to be any.
>
> My dim recollection is that a bipolar electrolytic is equivalent to
> back-to-back polarized electrolytics.  That is, you get twice the ESR &
> ESL, and some weirdness around 0-volts.  I'd be nervous if the current
> was appreciable.  However they've been used for many years in lots of
> applications, mostly in moderate-level coupling applications where
> distortion wasn't an issue.  Probably as reliable as a standard
> electrolytic.

back to back electros in // with back to back diodes for improved  
reliability

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#431166

On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin wrote:

> High-K ceramic caps are awful. They lose 90% of their capacitance at
> rated voltage.
> 
> Are bipolar aluminum caps reliable?
> 
> I would think that polymer aluminum caps would make good nonpolarized
> things, but there don't seem to be any.

A long time ago, just after a shake test, we found out that high-C 
ceramic materials are either piezo electric, or flexible enough to change 
capacitance with vibration.  Either way, they made dandy microphones.

Since the circuit in question had DC paths to ground on both sides of the 
cap, we replaced it with a pair of back-to-back tantalums with the far 
side biased through a high resistance to some negative voltage (probably 
-12V) that was already on the board.  It worked pretty good for a panic-
driven kludge.

Sumpin' to think about.

-- 
www.wescottdesign.com

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#431187

"Tim Wescott" <tim@seemywebsite.really> wrote in message 
news:ybmdnZ2Ne9JZtJ3FnZ2dnUU7-QGdnZ2d@giganews.com...
> Since the circuit in question had DC paths to ground on both sides of the
> cap, we replaced it with a pair of back-to-back tantalums with the far
> side biased through a high resistance to some negative voltage (probably
> -12V) that was already on the board.  It worked pretty good for a panic-
> driven kludge.
>
> Sumpin' to think about.

An excellently valid solution, and note that tantalums are precise enough 
(~10%) to avoid the problem mentioned a few posts above (reversal for 
mismatched caps in series).

Electrolytic caps (chemically speaking, this includes wet and dry tants) are 
basically semiconductor* junction diodes with a fuckoff huge junction area. 
Reverse bias is a natural win for them!

*All insulators are semiconductors, to a sufficient definition of "semi". 
:-)

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#431225

On Fri, 14 Oct 2016 03:43:27 -0500, Tim Williams wrote:

> *All insulators are semiconductors, to a sufficient definition of
> "semi". :-)

Perhaps in the sense of being partially conductive.  But not, I'm pretty 
sure, in the sense of being able to form a rectifying junction, much less 
a BJT or FET.

(I wonder if you could make a copper-oxide BJT -- I know it'll make a 
rectifying junction.)

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

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#431263

"Tim Wescott" <seemywebsite@myfooter.really> wrote in message 
news:lP2dnUuQQ7QNjpzFnZ2dnUU7-U-dnZ2d@giganews.com...
>> *All insulators are semiconductors, to a sufficient definition of
>> "semi". :-)
>
> Perhaps in the sense of being partially conductive.  But not, I'm pretty
> sure, in the sense of being able to form a rectifying junction, much less
> a BJT or FET.
>
> (I wonder if you could make a copper-oxide BJT -- I know it'll make a
> rectifying junction.)

Not counting chemical quirks, like non-stoichiometric compositions leading 
to uncontrollable doping (AFAIK, it's unreasonable to make N-type ZnO, 
because of excess oxygen?), and the different kinds of bandgap (direct vs. 
indirect), and some other things I forget -- it's just a matter of 
temperature.  A semiconductor is any old insulator with a conveniently low 
bandgap, sufficient to allow a usefully small amount of thermally freed 
charge carriers.

I want to say, transistors were first discovered in Cu2O, late 19th century. 
I can't seem to find a reference to it, though.  Lillenfeld made some 
interesting patents in the 20s, but they were poorly understood, and 
technically impossible, until years later (it took two score until FETs 
entered commercial use).

Without advanced materials science, and theoretical knowledge to back it up 
(you say it has to be HOW PURE!?), such observations were lucky 
coincidences, easily written off as shoddy work.

It's just as well; no existing infrastructure could have used them. 
ESD/surge from telegraph lines would've quickly toasted a point-contact 
transistor, if they even lasted long enough (between mechanical creep and 
atmospheric contamination) to perform any useful amplification in the first 
place.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#431168

On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>
>
>High-K ceramic caps are awful. They lose 90% of their capacitance at
>rated voltage.

How much capacitance do you need?
>
>Are bipolar aluminum caps reliable?
>
>I would think that polymer aluminum caps would make good nonpolarized
>things, but there don't seem to be any.

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#431170

On Thu, 13 Oct 2016 20:57:25 -0400, krw <krw@nowhere.com> wrote:

>On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin
><jjlarkin@highlandtechnology.com> wrote:
>
>>
>>
>>High-K ceramic caps are awful. They lose 90% of their capacitance at
>>rated voltage.
>
>How much capacitance do you need?

Tens of uF at 20 volts maybe. There's a lot of current drive
available, so a tantalum would be risky.



>>
>>Are bipolar aluminum caps reliable?
>>
>>I would think that polymer aluminum caps would make good nonpolarized
>>things, but there don't seem to be any.

-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

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

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#431174

On Thu, 13 Oct 2016 18:05:06 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Thu, 13 Oct 2016 20:57:25 -0400, krw <krw@nowhere.com> wrote:
>
>>On Thu, 13 Oct 2016 07:01:54 -0700, John Larkin
>><jjlarkin@highlandtechnology.com> wrote:
>>
>>>
>>>
>>>High-K ceramic caps are awful. They lose 90% of their capacitance at
>>>rated voltage.
>>
>>How much capacitance do you need?
>
>Tens of uF at 20 volts maybe. There's a lot of current drive
>available, so a tantalum would be risky.
>
X7Rs are available in that sort of capacitance/voltage in 1210s.
They're a bit pricey but some aren't that bad (C/V wise).

>
>>>
>>>Are bipolar aluminum caps reliable?
>>>
>>>I would think that polymer aluminum caps would make good nonpolarized
>>>things, but there don't seem to be any.

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#431188

"krw" <krw@nowhere.com> wrote in message 
news:smd00ct7cv3u6q5dcrdna651bb3rlt55uj@4ax.com...
>>>How much capacitance do you need?
>>
>>Tens of uF at 20 volts maybe. There's a lot of current drive
>>available, so a tantalum would be risky.
>>
> X7Rs are available in that sort of capacitance/voltage in 1210s.
> They're a bit pricey but some aren't that bad (C/V wise).

Or aluminum polymer (which, as with others: two in anti-series, with bias).

If you needed energy storage, C0G would be great.  It's just preposterously 
expensive, in any large value...

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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