[time-nuts] high rev isolation amps

John Ackermann N8UR jra at febo.com
Sat Mar 26 22:33:12 EDT 2016


In light of this discussion, I'm taking a deep gulp to mention a project 
that's finished but has been on my back burner for a while.

A few years ago I laid out a high isolation, low noise buffer amp based 
on one of Bruce's cascaded-transistor designs.  Isolation was measured 
in excess of 100dB with PN floor around -170dBc/Hz.  The frequency range 
is 1 MHz to 30 MHz and gain can be set from -10 to +7 dB.  It's designed 
for 18VDC input but will work at 13.8, with less headroom.  At 18V it 
can put out close to +20dBm.  It's a 1.75 x 3.75 inch board using SMT 
parts (nothing tiny, but *lots* of passives -- about 80 parts total).

The board is ready to go, but I wasn't sure if there would be enough 
interest to justify production.  Given the tedious surface mount 
assembly, I assumed that there wouldn't be much interest in a kit, and 
an assembly run requires at least 50, and preferably 100, units to get a 
reasonable price.  At 100 units, I hope the price for an assembled board 
could be below $100, but no guarantees.

If there is enough interest, TAPR could consider doing a production run. 
  If not, I'll release the design package including Gerbers.

I'll try to get some better documentation put together in the next week 
or two, and figure out a way to create a sign-up list for people who are 
interested.  We'd have to have a minimum number of committed orders 
before kicking things off.

John
----

On 03/26/2016 08:24 PM, jimlux wrote:
> On 3/26/16 4:14 PM, Richard (Rick) Karlquist wrote:
>> Nothing has come to my attention in the last
>> 35 years that is superior for buffer amplifiers
>> to the simple cascade of grounded base transistors
>> as described by numerous NBS/NIST papers.
>> The chain usually starts with a common emitter
>> (with emitter degeneration resistor), which
>> is an even older NBS classic.
>>
>> I realize you asked for an OTS connectorized
>> version.  Unfortunately, I have never seen
>> one of these offered in said 35 years.
>
> Yeah, i've spent a while looking through various catalogs..
>
> Odd that nobody sells one: sure, it's probably a limited market, but
> there's plenty of companies that sell limited market widgets (e.g. I'm
> surprised Wenzel doesn't sell one.. in the online catalog info, they
> don't even give S12 data of any kind)
>
>
>
>
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