[sdiy] HF VCOs and tracking problems

[Karl Ekdahl]

Okay there's a lot of good suggestions here. Yeah i'm trying to avoid the PLL stuff as i want both low parts count and i want to avoid the settling time. This is for testing some divide-down stuff so i need all of the usual properties of a VCO. I'm going to give the OTA triangle core a shot and see how good tracking i can get. I'll probably be back with more questions. Thanks a lot everyone!

Karl




----- Ursprungligt meddelande ----
Från: Oscar Salas <osalas at electronic-sea.net>
Till: Karl Ekdahl <elektrodwarf at yahoo.se>
Kopia: "synth-diy at dropmix.xs4all.nl" <synth-diy at dropmix.xs4all.nl>
Skickat: tisdag, 13 november 2012 13:04
Ämne: Re: [sdiy] HF VCOs and tracking problems

>> I'm trying to design a high frequency VCO, something that can span a
>> frequency range of ~6-200kHz. I'm basing it off of a standard sawtooth
>> core and i'm experiencing tracking problems. I realized this might be an
>> issue before i begun but i don't really understand what the underlying
>> problem is, nor the remedy.


> So, if the biggest culprit is the uneven charge/discharge time would i be
> better off using a different type of VCO core? Like a triangle wave core
> for instance?



If you use a triangle core and have tracking problems at high frequencies,
you could operate the triangle core at more low frequencies and pass the
triangle wave through several "Absolute Value Circuit" in series
compensating offset and amplitude. Each of one will double the frequency.


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