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tech / sci.electronics.design / Re: Looking for fast-ish sot-89 NPN

SubjectAuthor
* Looking for fast-ish sot-89 NPNGerhard Hoffmann
+- Re: Looking for fast-ish sot-89 NPNjlarkin
+* Re: Looking for fast-ish sot-89 NPNJohn Miles, KE5FX
|`- Re: Looking for fast-ish sot-89 NPNGerhard Hoffmann
+* Re: Looking for fast-ish sot-89 NPNjlarkin
|`* Re: Looking for fast-ish sot-89 NPNGerhard Hoffmann
| `- Re: Looking for fast-ish sot-89 NPNjlarkin
`- Re: Looking for fast-ish sot-89 NPNLM

1
Looking for fast-ish sot-89 NPN

<t5c4ha$arif$1@solani.org>

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From: dk4...@arcor.de (Gerhard Hoffmann)
Newsgroups: sci.electronics.design
Subject: Looking for fast-ish sot-89 NPN
Date: Tue, 10 May 2022 00:27:53 +0200
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 by: Gerhard Hoffmann - Mon, 9 May 2022 22:27 UTC

Hi,

I'm trying to build a 2-200 MHz isolation amplifier.

For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.

The circuit is a voltage to current converter, followed by a
double cascode.

2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
but brings me negative input impedance, gain peaks and so on.
I'm playing with the usual ferrite beads, but that does not
bring complete relief.

The emitter node of the v/i converter definitely wants to play
a capacitively loaded follower. I'm just making GND cutouts
in the layers under the emitter.

Is there a transistor abt. halfway in speed?
BFU590 etc is even faster.
Something flat like SOT-89 would be fine.
And I would not object 1 GHz BW if it comes without the side effects. :-)

Any ideas?

Cheers, Gerhard

Re: Looking for fast-ish sot-89 NPN

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Subject: Re: Looking for fast-ish sot-89 NPN
Date: Mon, 09 May 2022 19:49:55 -0700
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 by: jlar...@highlandsniptechnology.com - Tue, 10 May 2022 02:49 UTC

On Tue, 10 May 2022 00:27:53 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

>Hi,
>
>I'm trying to build a 2-200 MHz isolation amplifier.
>
>For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>
>The circuit is a voltage to current converter, followed by a
>double cascode.
>
>2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
>but brings me negative input impedance, gain peaks and so on.
>I'm playing with the usual ferrite beads, but that does not
>bring complete relief.
>
>The emitter node of the v/i converter definitely wants to play
>a capacitively loaded follower. I'm just making GND cutouts
>in the layers under the emitter.
>
>Is there a transistor abt. halfway in speed?
>BFU590 etc is even faster.
>Something flat like SOT-89 would be fine.
>And I would not object 1 GHz BW if it comes without the side effects. :-)
>
>Any ideas?
>
>Cheers, Gerhard

SOT-89s seem to be going out of style.

There are opamps that might do the whole thing for you. One of the THS
gadgets maybe. THS3091? TI makes some radical fast opamps.

--

Anybody can count to one.

- Robert Widlar

Re: Looking for fast-ish sot-89 NPN

<b1e4bacb-67a9-4003-90ee-626fd4f8bb70n@googlegroups.com>

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Subject: Re: Looking for fast-ish sot-89 NPN
From: jmi...@gmail.com (John Miles, KE5FX)
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 by: John Miles, KE5FX - Tue, 10 May 2022 22:28 UTC

On Monday, May 9, 2022 at 3:28:01 PM UTC-7, Gerhard Hoffmann wrote:
> Hi,
>
> I'm trying to build a 2-200 MHz isolation amplifier.
>
> For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.

Depending on power/noise requirements, THS3491 is a good way to go for
200 MHz and below. You can get +20 dBm out of it at 200 MHz, even after
losing 6 dB in a 50-ohm series termination.

-- john, KE5FX

Re: Looking for fast-ish sot-89 NPN

<t5ff45$bqch$1@solani.org>

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From: dk4...@arcor.de (Gerhard Hoffmann)
Newsgroups: sci.electronics.design
Subject: Re: Looking for fast-ish sot-89 NPN
Date: Wed, 11 May 2022 06:47:01 +0200
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 by: Gerhard Hoffmann - Wed, 11 May 2022 04:47 UTC

Am 11.05.22 um 00:28 schrieb John Miles, KE5FX:
> On Monday, May 9, 2022 at 3:28:01 PM UTC-7, Gerhard Hoffmann wrote:
>> Hi,
>>
>> I'm trying to build a 2-200 MHz isolation amplifier.
>>
>> For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>
> Depending on power/noise requirements, THS3491 is a good way to go for
> 200 MHz and below. You can get +20 dBm out of it at 200 MHz, even after
> losing 6 dB in a 50-ohm series termination.
>
> -- john, KE5FX

I remember when it came out I proposed it on Time Nuts under
the name "LMH6702 on steroids" and IIRC it did not find much
enthusiasm.

This here is more a leisure time project, to convert a former
NIST-like design by un-PNP-ing it and getting along with 12V Vcc
without resorting to folded cascodes.

S22 is already quite OK, but gain == S21 has an unwanted peak
that comes from the V/I converter. It is dangerous to
stability. I can reduce it to 5 dB with a damping resistor in
parallel to one of the beads, but this is experimental voodoo.

<
https://www.flickr.com/photos/137684711@N07/52064373427/in/dateposted-public/
>

I could use more ferrite on the input, but at frequencies
where the beads create resistance, they also create thermal
noise.

Cheers, Gerhard

Re: Looking for fast-ish sot-89 NPN

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Subject: Re: Looking for fast-ish sot-89 NPN
Date: Wed, 11 May 2022 07:05:53 -0700
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 by: jlar...@highlandsniptechnology.com - Wed, 11 May 2022 14:05 UTC

On Tue, 10 May 2022 00:27:53 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

>Hi,
>
>I'm trying to build a 2-200 MHz isolation amplifier.
>
>For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>
>The circuit is a voltage to current converter, followed by a
>double cascode.
>
>2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
>but brings me negative input impedance, gain peaks and so on.
>I'm playing with the usual ferrite beads, but that does not
>bring complete relief.
>
>The emitter node of the v/i converter definitely wants to play
>a capacitively loaded follower. I'm just making GND cutouts
>in the layers under the emitter.
>
>Is there a transistor abt. halfway in speed?
>BFU590 etc is even faster.
>Something flat like SOT-89 would be fine.
>And I would not object 1 GHz BW if it comes without the side effects. :-)
>
>Any ideas?
>
>Cheers, Gerhard

If you don't need a lot of swing, use a cheap MMIC.

Here's a signal pickoff amp with very high reverse isolation. Big
passive attenuator, then lots of gain.

https://www.dropbox.com/s/dbekbobus1k8by3/T503_Mon_Pickoff.jpg?dl=0

That opamp has a fixed gain of 5 and 2.4 GHz bw. There's a version
with g=10 and 1.8 GHz.

--

Anybody can count to one.

- Robert Widlar

Re: Looking for fast-ish sot-89 NPN

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From: sala.n...@mail.com (LM)
Newsgroups: sci.electronics.design
Subject: Re: Looking for fast-ish sot-89 NPN
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 by: LM - Thu, 12 May 2022 22:02 UTC

On Tue, 10 May 2022 00:27:53 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

>Hi,
>
>I'm trying to build a 2-200 MHz isolation amplifier.
>
>For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>
>The circuit is a voltage to current converter, followed by a
>double cascode.
>
>2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
>but brings me negative input impedance, gain peaks and so on.
>I'm playing with the usual ferrite beads, but that does not
>bring complete relief.
>
>The emitter node of the v/i converter definitely wants to play
>a capacitively loaded follower. I'm just making GND cutouts
>in the layers under the emitter.
>
>Is there a transistor abt. halfway in speed?
>BFU590 etc is even faster.
>Something flat like SOT-89 would be fine.
>And I would not object 1 GHz BW if it comes without the side effects. :-)
>
>Any ideas?
>
>Cheers, Gerhard
I wonder if some SOT89 transmitter Fet would work. Some are stable
from here to there, and fast too. AFT something

Re: Looking for fast-ish sot-89 NPN

<t5khjl$eifi$1@solani.org>

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From: dk4...@arcor.de (Gerhard Hoffmann)
Newsgroups: sci.electronics.design
Subject: Re: Looking for fast-ish sot-89 NPN
Date: Fri, 13 May 2022 05:00:05 +0200
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 by: Gerhard Hoffmann - Fri, 13 May 2022 03:00 UTC

Am 11.05.22 um 16:05 schrieb jlarkin@highlandsniptechnology.com:
> On Tue, 10 May 2022 00:27:53 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
> wrote:
>
>> Hi,
>>
>> I'm trying to build a 2-200 MHz isolation amplifier.
>>
>> For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>>
>> The circuit is a voltage to current converter, followed by a
>> double cascode.
>>
>> 2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
>> but brings me negative input impedance, gain peaks and so on.
>> I'm playing with the usual ferrite beads, but that does not
>> bring complete relief.
>>
>> The emitter node of the v/i converter definitely wants to play
>> a capacitively loaded follower. I'm just making GND cutouts
>> in the layers under the emitter.
>>
>> Is there a transistor abt. halfway in speed?
>> BFU590 etc is even faster.
>> Something flat like SOT-89 would be fine.
>> And I would not object 1 GHz BW if it comes without the side effects. :-)
>>
>> Any ideas?
>>
>> Cheers, Gerhard
>
> If you don't need a lot of swing, use a cheap MMIC.
>
> Here's a signal pickoff amp with very high reverse isolation. Big
> passive attenuator, then lots of gain.
>
> https://www.dropbox.com/s/dbekbobus1k8by3/T503_Mon_Pickoff.jpg?dl=0
>
> That opamp has a fixed gain of 5 and 2.4 GHz bw. There's a version
> with g=10 and 1.8 GHz.

When I want to measure phase noise at -170 dBc @ 100 MHz
with cross correlation and tricks, then I cannot start with an
attenuator that puts everything into thermal noise.

On the output of my PLL it's different. At 10 GHz, it's not
that hard. You don't need to swimm faster than the sharc, it's
enough to swimm faster than the guy next to you. Ie, the
dynamic range is already pretty much reduced and worse
oscillators in absolute terms will do for the stereo downmixing
to the cross correlation thing.

I just want to see the best my crystal oscillators can do @ ~100MHz.

Cheers, Gerhard

Re: Looking for fast-ish sot-89 NPN

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 by: jlar...@highlandsniptechnology.com - Fri, 13 May 2022 16:34 UTC

On Fri, 13 May 2022 05:00:05 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

>Am 11.05.22 um 16:05 schrieb jlarkin@highlandsniptechnology.com:
>> On Tue, 10 May 2022 00:27:53 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
>> wrote:
>>
>>> Hi,
>>>
>>> I'm trying to build a 2-200 MHz isolation amplifier.
>>>
>>> For 13 dBm I need abt. 120 mA peak current, 70 mA quiescent.
>>>
>>> The circuit is a voltage to current converter, followed by a
>>> double cascode.
>>>
>>> 2N3904 is too slow, BFQ19S is too hot, it would do 1 GHz,
>>> but brings me negative input impedance, gain peaks and so on.
>>> I'm playing with the usual ferrite beads, but that does not
>>> bring complete relief.
>>>
>>> The emitter node of the v/i converter definitely wants to play
>>> a capacitively loaded follower. I'm just making GND cutouts
>>> in the layers under the emitter.
>>>
>>> Is there a transistor abt. halfway in speed?
>>> BFU590 etc is even faster.
>>> Something flat like SOT-89 would be fine.
>>> And I would not object 1 GHz BW if it comes without the side effects. :-)
>>>
>>> Any ideas?
>>>
>>> Cheers, Gerhard
>>
>> If you don't need a lot of swing, use a cheap MMIC.
>>
>> Here's a signal pickoff amp with very high reverse isolation. Big
>> passive attenuator, then lots of gain.
>>
>> https://www.dropbox.com/s/dbekbobus1k8by3/T503_Mon_Pickoff.jpg?dl=0
>>
>> That opamp has a fixed gain of 5 and 2.4 GHz bw. There's a version
>> with g=10 and 1.8 GHz.
>
>When I want to measure phase noise at -170 dBc @ 100 MHz
>with cross correlation and tricks, then I cannot start with an
>attenuator that puts everything into thermal noise.

OK. I have 6.5 volts of signal driving an e/o modulator. The pickoff
is just for a front-panel scope monitor.

--

Anybody can count to one.

- Robert Widlar

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