Re: Fast monostable with a transistpor array

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:
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"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:
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"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.
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It offers three 8GHz NPN parts and two 5.5GHz PNP parts in a single array.
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https://www.renesas.com/us/en/document/dst/hfa3046-hfa3096-hfa3127-hfa3128-datasheet?r=494216
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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.
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That is neither fast nor a monostable.

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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.

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It doesn't work!
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There's no reason to use many-GHz parts in micropower circuits. One
reason is that the sim breaks.

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Most versions of the HFA3046 are obsolete. The only one left at
Digikey costs $12. It would be risky to design around that part.

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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.
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Wasn't  HFA originally a Harris part?
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There are lots of dual (non-monolithic) diodes and bipolars and fets
around, but the monolithic arrays are mostly gone.

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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?

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The duals save space, but aren't well matched so are electrically and
thermally equivalent to buying two separate parts.
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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.

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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.