[time-nuts] LT3042, etc. Re: HP E1938A schematics.

[Bob kb8tq]

Hi

All capacitors have series inductance as well as resistance. As you go past about
100 KHz or so, this gets to be very noticeable. Exact details will always vary with
capacitor type and size. 

Modern switchers (just like modern  logic gates) run ever faster edge rates. The faster 
the switch, the more high frequency energy in the edge. A switcher running at 2 MHz 
and doing 90% efficiency will probably need a switching speed faster than 10 ns. 

This all just keeps pushing the PSRR requirements up and up in frequency. 

Bob

> On Jul 9, 2019, at 1:30 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
>>> Not only are they low noise, but they have spectacularly good HF 
>>> rejection across the regulator up to 10s of MHz.
> 
>> In the 5071A, I wanted high bandwidth PSRR and stumbled across a designer's
>> manual (HP internal document) for the MMS Modular Measurement System.  They
>> described a regulator with a common base pass transistor and an op amp, with
>> a bandwidth approaching 1 MHz. 
> 
> I'm used to thinking that the bypass caps on the board will take care of high 
> frequencies.
> 
> What's the advantage of a PSRR in the MHz range?  Is it as simple as reducing 
> the number and size of the caps needed?
> 
> In this area, is there a significant difference between analog and digital 
> sections?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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