[sdiy] DAC/REF Data sheet / Dev board R question

[rsdio at audiobanshee.com]

This case has a maximum ESR of 1R5, but I'm glad you brought up the minimum ESR case.

I went looking for the frequency response of a series resistor and capacitor, but all I ever see is the first order RC combination that is series resistor and shunt capacitor. What is the frequency response of a shunt that's comprised of a series resistor and capacitor to ground? I haven't bothered to derive the math, but I suppose it's technically flat if all you have is the two passive components - where it becomes frequency dependent is the interaction with the connected circuits before or after. Typically, that would be the feedback path of a gain stage. Anyone care to comment?

Brian


On Apr 25, 2015, at 9:25 PM, Paul Perry <pfperry at melbpc.org.au> wrote:
> I don't know about this particular case, but sometimes you DO need a series resistor on the output cap, strange as it might seem.
> Some regulators expect the output capacitor to have an ESR within certain bounds - see for example app note
> http://www.ti.com/lit/an/snva558/snva558.pdf .  Note that for a given cap, ESR varies with temperature.
> I hate to think of the number of times I had designs behave inextricably weirdly due to neglecting to pay attention
> to the regulator specs.
> Although three terminal regs are available very cheaply indeed from practically anywhere, they are one of
> the components that I find worth buying from recognised manufacturers.
> 
> It's nice that we can get regulators today with all manner of specs - but all this cunning design comes at the cost
> of having to pay close attention to the app notes.
> 
> paul perry Melbourne Australia
> 
> ----- Original Message ----- From: <rsdio at audiobanshee.com>
>> I say that you not only can safely get rid of this resistor, but that you should get rid of it! I don't see how it can do anything but harm.