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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: fast NPN in LT Spice
Date: Tue, 4 Jun 2024 00:27:33 +1000
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On 3/06/2024 5:50 pm, piglet wrote:
> john larkin <jl@650pot.com> wrote:
>> On Sun, 2 Jun 2024 20:35:02 -0400, "Edward Rawde"
>> <invalid@invalid.invalid> wrote:
>>
>>> "john larkin" <jl@650pot.com> wrote in message
>>> news:4n2q5jln0sb9oqbfp81jm723tbjf7tol80@4ax.com...
>>>> On Sun, 2 Jun 2024 19:46:14 -0400, "Edward Rawde"
>>>> <invalid@invalid.invalid> wrote:
>>>>
>>>>> "john larkin" <jl@650pot.com> wrote in message
>>>>> news:eqsp5jde87vqs6du4a7djoalag7kpkuhkr@4ax.com...
>>>>>> There are many NPNs in the standard LT Spice library.
>>>>>>
>>>>>> Does anyone know of a fast, RF type, transistor? It's hard to tell
>>>>>> from the jillion lines of fine-print parameters.
>>>>>
>>>>> https://www.google.com/search?q=".model+BFR92A"
>>>>>
>>>>>>
>>>>>> I want to make a model of the MC10EP89 gate.
>>>>>>
>>>>>
>>>>
>>>> That doesn't seem to be in the LT Spice library.
>>>>
>>>> 2SC3838K looks OK.
>>>>
>>>> It's hard to pick parts, discrete or ICs, from the library.
>>>
>>> Yes it would be nice if a description of the part as well as the part
>>> number could be included.
>>
>> A sortable column of Ft would be nice for transistors. Lacking that,
>> sorting on Vce helps spot the RF parts. Low voltage suggests RF.
> 
> Ft isn’t one of the model parameters, guess you have to look for low Tf and
> Tr transit times or low junction capacitances?

Or you can look at wide-band transistors, pick one and plug the 
manufacturers Spice model into LTSpice yourself, which is something I've 
done from time to time (and posted the .asc files here), and John Larkin 
doesn't seem to be able to manage.

He's just described the example I pulled out of the circuit file on my 
computer as "hideous mess", which is inaccurate. Nobody would use +/-15V 
rails to drive just that circuit, but if +/-15V rails are what you have 
got, that circuit could solve a specific problem.

-- 
Bill sloman, Sydney