Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: fast NPN in LT Spice
Date: Fri, 07 Jun 2024 09:24:10 -0400
Organization: A noiseless patient Spider
Lines: 60
Message-ID: <on166jteri1u6ihlh2eh297akpjnif7oln@4ax.com>
References: <v3j087$1bpc$1@nnrp.usenet.blueworldhosting.com> <4n2q5jln0sb9oqbfp81jm723tbjf7tol80@4ax.com> <v3j33n$2dk5$1@nnrp.usenet.blueworldhosting.com> <gkdq5jdq7gbe9pd5qekn1evt2gaa8unqhj@4ax.com> <v3jqnn$3prrc$1@dont-email.me> <ikir5jdbv9rbponup9btn3bcfsm5326ea2@4ax.com> <v3kiso$3u1if$1@dont-email.me> <q9a26jdroatud3o1hgaqve5r4bc6got063@4ax.com> <v3scus$1gr7m$1@dont-email.me> <nmt36j9bm5ohrjla58o7e2kg7pvhbtr0e3@4ax.com> <v3u0qd$1tric$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Date: Fri, 07 Jun 2024 15:22:20 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="5c237af29571365e6622c78b822cdd99";
	logging-data="2201441"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18DjPMxxNHkbMTlG2b6qewB"
Cancel-Lock: sha1:EjU6GQHRYe7W/2PnGiyOzvxf3jU=
X-Newsreader: Forte Agent 4.2/32.1118
Bytes: 3638

On Fri, 7 Jun 2024 14:03:16 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:

>On 7/06/2024 4:05 am, legg wrote:
>> On Thu, 6 Jun 2024 23:18:12 +1000, Bill Sloman <bill.sloman@ieee.org>
>> wrote:
>> 
>>> On 6/06/2024 1:46 pm, legg wrote:
>
><snip>
>
>> It's difficult to isolate a model parameter or product of parameters
>>   that predict the performance demonstrated in this simulation.
>> 
>> Oscillators seem to have ( ~ mostly) high Rbb, which is
>> device-specific. . . . but also lower ( 1/100) IKR, which you'd
>> think was irrelevant.
>> 
>> Bf, Tr, Tf and capacitances don't stand out.
>> 
>> I suppose you'd need to look at the numbers separating astable from
>> monostable operation. You wouldn't want an unspecified component
>> characteric to dominate basic circuit function.
>
>You don't get the choice, unless you are in the position of developing a 
>new transistor for a new market.
>
>Most of us are in the position of finding a transistor which we can buy 
>-  preferably off the shelf - which we can use to do a specific job.
>
>The options tend to be pretty restricted. There are a lot fewer 
>broad-band transistors on the market than there used to be.
>
>The manufacturer's Spice model give us the option of modelling a circuit 
>which might work in some version of Spice, and tweaking the circuit to 
>get the simulation to perform our job tolerably well.
>
>We can't sell the simulation - customers want real circuits that work in 
>real life.
>
>-- 
>Bill Sloman, Sydney

That's sort of what I'm talking about. You choose a part, you choose a
model, you choose a parameter that allows a model to simulate 
performance more accurately. You choose a circuit configuration 
with component values.

From the larger spreadsheet, you see models for 'similar devices
varying widely in performance in a particular circuit configuration.

So what is it, in the model, or in the circuit configuration, that 
allows such a wide variation in performance. What parameter is a 
true predictor? What weakness in the circuit is the wild card?

Looking for understanding or beneficial increase in knowledge here.
Not pushing or pulling the benefits or disadvantages of modeling 
or breadboarding - already have pretty fixed opinions about that.

RL