VCOs

[Mikko Helin]

Hello,

Are there any VCOs that produce saw waveform by recharging the
cap instead of discharging it as usual? I mean something like
this: http://www.uta.fi/~helin/sch/s-vco.gif. Usually in
relaxation type ocillator the cap discharge time has to
be constant, discharge can't be detected by comparator,
but in this case the charging can be detected (here by the schmitt-
trigger, but comparators could be used as well). Are there any problems
with this kind of method (like temperature or supply dependency,
possible current spikes etc.).

-Mikko