[sdiy] exponential vs linear vco cores

[cheater cheater]

Antti,
thanks for the round up, that was a good bit of info as usual from you.
How are the different V/I built?

D.

On Fri, Feb 26, 2010 at 12:20, Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
> On Fri, 26 Feb 2010, cheater cheater wrote:
>
>> I was wondering if someone knows a good article on the differences
>> between exponential core and linear core VCOs?
>> What is the difference in how they operate?
>
> The core itself is the same for both types, only the V -> I converter
> differs. Exponential has inherently wide range, zero/low per hz offset but
> suffers from heavy temperature dependency on CV scale factor (needing tempco
> resistor or other compensation). Linear has low tempco but needs trimming to
> get rid of constant per hz offset and can't as easily get as wide range.
> Linear is much harder to modulate (such as for vibrato) as modulations must
> be of the form y = x*2^(mod) and the exponent operation must be temperature
> compensated such that zero modulation will always mean no DC scaling by
> temperature (to avoid detuning with temperature).
>
> For digital control I consider linear VCOs to be better bang for the buck as
> you don't need to bother with tempco and can trim any offsets digitally.
>
> Antti
>
> "No boom today. Boom tomorrow. There's always a boom tomorrow"
>  -- Lt. Cmdr. Ivanova
>