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NNTP-Posting-Date: Fri, 14 Jun 2024 16:33:43 +0000
From: john larkin <jl@650pot.com>
Newsgroups: sci.electronics.design
Subject: Re: Fast monostable with a transistpor array
Date: Fri, 14 Jun 2024 09:33:43 -0700
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On Fri, 14 Jun 2024 12:18:23 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:

>"john larkin" <jl@650pot.com> wrote in message news:8epo6jhf5k5nbkkqp5ot9b6nq1lhoia870@4ax.com...
>> On Fri, 14 Jun 2024 11:08:56 -0400, "Edward Rawde"
>> <invalid@invalid.invalid> wrote:
>>
>>>
>>>"john larkin" <jl@650pot.com> wrote in message news:hilo6j9dgctalpiu4v09rpdavf6fetm1cv@4ax.com...
>>>> On Thu, 13 Jun 2024 23:25:37 -0400, "Edward Rawde"
>>>> <invalid@invalid.invalid> wrote:
>>>>
>>>>>"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:v4f2nm$2augj$1@dont-email.me...
>>>>>> One option John Larjkin doesn't seem to have explored is using Renesas HFA3096 five transistor array as basis for his
>>>>>> mononstable
>>>>>> and level shifter.
>>>>>>
>>>>>> It offers three 8GHz NPN parts and two 5.5GHz PNP parts in a single array.
>>>>>>
>>>>>> https://www.renesas.com/us/en/document/dst/hfa3046-hfa3096-hfa3127-hfa3128-datasheet?r=494216
>>>>>>
>>>>>
>>>>>I put the NPN model parameters into a circuit designed by yourself.
>>>>>It's late now but I got as far as Time step too small.
>>>>>
>>>>
>>>> That is neither fast nor a monostable.
>>>
>>>Yes ok it's an astable and certainly not intended to be fast.
>>>It was intended only to see if the model worked. Nothing more.
>>
>> It doesn't work!
>>
>>>
>>>>
>>>> There's no reason to use many-GHz parts in micropower circuits. One
>>>> reason is that the sim breaks.
>>
>> Most versions of the HFA3046 are obsolete. The only one left at
>> Digikey costs $12. It would be risky to design around that part.
>
>If it's obsolete or going obsolete then yes it would make no sense to use it.
>I would guess that you get to do plenty of work because a manufacturer has suddenly decided to discontinue a part.
>
>> Wasn't  HFA originally a Harris part?
>>
>> There are lots of dual (non-monolithic) diodes and bipolars and fets
>> around, but the monolithic arrays are mostly gone.
>
>What part would you recommend (single or dual) and does it have a working LTSpice model?

Just pull up some parts from the standard library, some low current
NPNs like BC547 maybe. Look for low capacitances if you care about
that; the HFAs are good in that respect.

Why do people avoid making clean 4-wire connections on schematics?

>
>>
>> The duals save space, but aren't well matched so are electrically and
>> thermally equivalent to buying two separate parts.
>>
>> I wonder if one could design really fast stuff with the HFA3046.
>> Package parasitics look nasty. And the big package will force ugly PCB
>> routing. You can plop a single tiny transistor wherever you want.
>
>Yes that is certainly an advantage of single transistors.
>Is a suitable single transistor still available for use in new designs?


There are zillions of single transistors around. I like BCX70 as an
npn gumdrop, although I use mosfets more often for simple things.