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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: 50 ohm termination
Date: Fri, 21 Mar 2025 15:38:52 +1100
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On 21/03/2025 9:27 am, Toaster wrote:
> On Thu, 20 Mar 2025 16:28:38 +1100
> Bill Sloman <bill.sloman@ieee.org> wrote:
> 
>> On 20/03/2025 12:55 pm, Toaster wrote:
>>> On Thu, 20 Mar 2025 01:41:29 +1100
>>> Bill Sloman <bill.sloman@ieee.org> wrote:
>>>
>>>> On 19/03/2025 9:23 pm, Toaster wrote:
>>>>> On Tue, 18 Mar 2025 19:01:51 -0700
>>>>> john larkin <jlArbor.com> wrote:
>>>>>
>>>>>> On Tue, 18 Mar 2025 18:59:44 -0400, Toaster <toaster@dne3.net>
>>>>>> wrote:
>>>>>>
>>>>>>> On Tue, 18 Mar 2025 16:02:45 -0700
>>>>>>> john larkin <jl@glen--canyon.com> wrote:
>>>>>>>
>>>>>>>> On Tue, 18 Mar 2025 18:29:42 -0400, Toaster <toaster@dne3.net>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> On Mon, 17 Mar 2025 19:17:13 -0700
>>>>>>>>> john larkin <jlArbor.com> wrote:
>>>>>>>>>
>>>>>>>>>> On Mon, 17 Mar 2025 19:50:17 -0400, Toaster
>>>>>>>>>> <toaster@dne3.net> wrote:

<snip>

> That driver is so tiny I'm wondering if the 10Mhz switching speeds are
> worth it! Researching some strange field interactions so I needed
> something that could switch a decent voltage (300V) at repetition rates
> close to 10Mhz. Odd requirements but until I can narrow down parameters
> I need to sweep up the frequency range as far as I can.

300V is a lot.

When I was blanking and unblanking an an electron beam in a electron 
microscope, the fast version - which turned the beam on for just 0.5nsec 
with 100psec transition times - only generated +/-7.5V.

The slow version - in an electron beam microfabricator - had to swing 
from 60V to OV at up to 10 MHz, because we couldn't get the blanking 
plates all that close to the beam in the electron beam microfabrictor 
(which was a million dollar machine, and we only sold a handful per year 
- ten per year in the good year).

300V shouldn't be all that difficult, but getting it to happen fast 
means charging up the capacitances in the MOSFET switch calls for quite 
a lot of current, and turning it on and off even faster.

-- 
Bill Sloman, Sydney