Re: fast NPN in LT Spice

On 12/06/2024 11:00 pm, legg wrote:

On Wed, 12 Jun 2024 16:30:02 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

On 12/06/2024 1:27 am, legg wrote:

On Wed, 12 Jun 2024 00:35:59 +1000, Bill Sloman <bill.sloman@ieee.org wrote:

On 11/06/2024 7:27 am, legg wrote:

On Sat, 8 Jun 2024 03:29:11 +1000, Bill Sloman <bill.sloman@ieee.org wrote:

On 7/06/2024 11:24 pm, legg wrote:

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>

The only parameters that I see in the ECLTN0E model that differs from
it's 'grouping', is a half order magnitude reduction in all junction
capacitances - this feature acting to prevent oscillatory behavior,
monostable or otherwise. It's ECL companion models oscillate (astable)
generally, despite Rbb parameters ranging over two orders of
magnitude, in this circuit configuration.

The broad-band transistors - of which the BFR92 is the most obvious example - famously have low collector base feedback capacitance, and a very thin base layer (2V base to emitter breakdown voltage).
Looking at the parameters, without thinking about the transistor behaviour that that they are intended to model, isn't a constructive or useful activity.
When I was working for Cambridge Instruments were selling the EBMF10.5 electron beam microfabricator to write the fine-line masks that made those sorts of devices.
Sometimes they were used to direct-write very fine features on particularly exotic (and expensive) devices. On one occasion the acceptance test for the machine was to write three wafers full of devices, which - when diced and package - would have paid for  the million-odd dollar price of the machine.
--
Bill Sloman, Sydney
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