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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Fast monostable with a transistpor array
Date: Fri, 14 Jun 2024 12:44:33 -0400
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"john larkin" <jl@650pot.com> wrote in message news:viro6jlt7h02ehbsq20em8uv5snn3736up@4ax.com...
> 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.

Yes but BC547 sounds almost as ancient as BC107
Are they still in production?
What would work well at a GHz or two or more?

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

Some places have rules about that.
I had trouble once, even though I put a very obvious and big blob where the join should have been.
When doing schematics of my own I prefer to avoid a one-blob 4-wire join. Use two blobs.

>
>>
>>>
>>> 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.
>