[R-390] OT: Ramp Generators

[Roy Morgan]

Barry,

Some bits in reply - hopefully useful:

The usual capacitor charging curve shown in texts and explanations assumes (usually states) that the charging current comes through a fixed resistor from a steady voltage source. We see the familiar exponential curve approaching the source voltage as time goes on. 

BUT in ramp generators there is usually a constant CURRENT source. This produces a linear voltage change with time on the cap. 

Tektronix produced a number of explanatory documents related to their oscilloscopes, and I am sure one of them tells about time bases. I can send more info on that later but in the meantime search for “tekwiki”:
W140.com/tekwiki/wiki ... main page, scroll way down to find “Concept Series”. 

The Tektronix folks were/are masters at ramp generators. 

Roy sends.

> On Apr 26, 2019, at 11:01 AM, Barry <n4buq at knology.net> wrote:
> 
> Hopefully this isn't too dumb of a question, but I was wondering how ramp (sawtooth) generators work ...
> 
> This is confusing to me.  Capacitors don't charge linearly, do they, and, if that's true, then why is the ramp linear wrt time?