Hysteresis without Feedback - Page 3

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Re: Hysteresis without Feedback
On Friday, July 14, 2017 at 8:25:36 PM UTC-7, snipped-for-privacy@notreal.com wrote:
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[about a Schmitt trigger]
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Outputs are NOT a function of inputs alone when the input is in the
hysteresis region.

There's stored charge, in the base of the turned-on transistor,
that holds the state.   That feedback loop is unstable without the
stored charge limiting the slew rate.   If you model the base Rbb and  
capacitance, you can initialize it so Spice always starts it up in your preferred
state when the input is in the hysteresis region.

Re: Hysteresis without Feedback

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In LTspice: .IC V(Q1B) = XX volts

Re: Hysteresis without Feedback
wrote:

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Then it's not a Schmitt, it's a latch.

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Don't be absurd.

Re: Hysteresis without Feedback
On Saturday, July 15, 2017 at 6:03:32 AM UTC-7, snipped-for-privacy@notreal.com wrote:
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A latch (Eccles-Jordan bistable circuit) is a two-transistor circuit
with positive feedback (collector-to-base coupling).   A Schmitt is a two-transistor
circuit with positive feedback (emitter coupling).    

Both are bistable, both have hysteresis.   The bistable nature implies
an INTERNAL state, which is why hysteresis in a latch implements memory,
as does hysteresis in a magnetic core or a Schmitt trigger.

The similarities are profound, the differences are... minor details.

Re: Hysteresis without Feedback
On Saturday, 15 July 2017 04:13:23 UTC+1, snipped-for-privacy@notreal.com  wrote:
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Wherever do you get that from?

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I thought you were asking about a transformer core. Your question was excessively vague.

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What is your point?


NT

Re: Hysteresis without Feedback
On Sat, 15 Jul 2017 04:12:09 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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I thought you were following the thread.  I guess that's too much to
expect.

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Re: Hysteresis without Feedback
On Saturday, 15 July 2017 14:04:22 UTC+1, snipped-for-privacy@notreal.com  wrote:
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I am. But I don't read minds. Your question was so vague it was hopeless.


NT

Re: Hysteresis without Feedback
On Sat, 15 Jul 2017 12:54:56 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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[snip]

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Where did bird-brain krw get that idea?  The 'subject at hand' is
hysteresis.  And he can't even spell 'Schmitt' ;-)

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Yup.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Hysteresis without Feedback
On Thu, 13 Jul 2017 22:46:26 -0400, snipped-for-privacy@notreal.com wrote:

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Only for shallow thinkers >:-}
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
We've slightly trimmed the long signature. Click to see the full one.
Re: Hysteresis without Feedback
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I could see something analogous to an over-centre latch, e.g. a diff pair with a lambda diode collector load. That just has local feedback. ;)  

Cheers

Phil Hobbs

Re: Hysteresis without Feedback
On Thursday, July 13, 2017 at 7:23:05 PM UTC-7, snipped-for-privacy@gmail.com wrote:
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Any latch has an internal state: the stored base charge in a saturated transistor,
for instance.    Thermal noise would reset the latch otherwise.

Re: Hysteresis without Feedback
On Thu, 13 Jul 2017 19:22:58 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Tunnel diode.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Hysteresis without Feedback
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Is there a Spice tunnel diode device?

Cheers

Phil "owner of a bag of 1mA TDs that are too slow to be useful" Hobbs

Re: Hysteresis without Feedback
On Thu, 13 Jul 2017 20:42:38 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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That must be hard to sign on checks.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Hysteresis without Feedback
snipped-for-privacy@gmail.com wrote:

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Not native. However, bordodynov has uploaded models to Yahoo LTspice.

See
https://groups.yahoo.com/neo/groups/LTspice/search/files?query=tunnel%
20diode

Download zip file:

TUNNEL_Diode.zip 4KB
New models and test
bordodynov May 23


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