Env vco!

[BJ]

Magnus Danielson wrote:
> 
> >>>>> "B" == BJ  <zzynt at swipnet.se> writes:
> 
>  B> Many years ago needed a VCO with a saw wave,and i
>  B> found a way to do this using a 4046 PLL.
> 
> BJ, you forgot to put a value on R11. I suggest a 100k.

Sorry i forgot, the value depends on the range you want to use.
100k is fine. 
 
> Also, why don't you let the cursuit take more of all that space?
> I try to scale up my schematics when they don't take that much space.

Because im lacy. :)

> 
>  B> And the MC202 and SH101 envelopgenerator and a simple VCO are found at:
>  B> http://home8.swipnet.se/~w-88660/schpcb.htm
> 
> For those that wishes to use an exponential cursuit with the 4046 VCO
> may hook it in on the current input of pin 12. This input wishes to
> see a current being drawn towards ground, so hooking it to the current
> output of a standard dual-transistor expo-cursuit (like the ASM-1 for
> instance) should go well.

Yes you may do so, i have , but the linearity is no good, One may use
the HC7046 who has even better linearity, i think it was approx 0.15%.
 
> Also, you may still use the VCO input for a real linear input (pin 9).

Yes again, this is good, i dont have to explain my own designs 
Magnus does it wery well indeed, great i can keep doing my 
lacy ,sleepy things here! :)

> The old CMOS versions of this VCO would scream up to 0.8-2.4 MHz
> (depending on powersupply), the newer onces get even higher. So, to
> get a pretty good responce one should consider pretty quick op-amps.
> The reset time is quite small, but if one would find it a trouble,
> then you could allways add the Franco compensation resistor in series
> with capacitor.
 
> The upside about using the 4046 as a core for a VCO is that you get
> the reset-cursuit for free as well as phase detectors to make PLL
> loops, in case you would fancy that game. BJ reused one of those to
> make a MS-20 style ringmod.

Yes again, wery nice thanks for the "going thru" my designs, ooh i think 
i have a cup of teee, and a smorgas while you other listening to Magnus
.:) 
 
> Oh, be carefull about loading the capacitor, use high-impedance
> op-amps (about 1 Tohm). 

Yes that right, or one may use FET's as buffers.
The frequency will shift down a bit if the cap is loaded to much.
When i did this design, it was for a pecussion synt voice,
I was just measuring around, and foundout about the charging
phases for the VCO and saw then the possibility to have a SAW wave.

Pitty that the EN pin dont reset the charging phase of the cap!

Regards
Haddock!