MOTM

As the old late-night talk show dialog would go...

"Heh heh heh... YES!!!  Heh heh heh..."
"That's some weird shtuff."

--PBr

> -----Original Message-----
> From:	Paul Schreiber [SMTP:synth1@...]
> Sent:	Saturday, October 14, 2000 7:32 PM
> To:	MOTM listserv
> Subject:	[motm] Is this useful?
> 
> On the VC Pulse Divider from Serge, there is an output called 'STEPPED'.
> I'm
> am pretty sure
> how they did it (not seeing the circuit).
> 
> The output is a stair-cased, positive-going sawtooth. The sawtooth is
> generated by a 5-bit
> counter, that is *clocked* by the input pulses and *reset* by the
> divide-by-N pulse.
> The output counter bits feed a 5-bit DAC.
> 
> So, here are some interesting things about this sawtooth:
> 
> a) for a fixed frequency in, the *amplitude* is inversly proportional to
> the
> divide ratio. Think
> about it: the longer you count, the higher the amplitude.
> 
> b) of course, for a fixed input frequency, the *output* frequency is
> proportional to the divide
> ratio. If you input 4Khz and divide by 8, you get out a 500Hz sawtooth
> with
> 8 steps. Assuming
> a -5V to +5V output scaling (like all the other signal generators), we
> have
> 10V/32 steps = 312mv/step. So for 8 steps = -5V to -2.5V sawtooth.
> 
> For straining the brain more: this acts as a low-pass filter! Since the
> divide ratio is a control
> voltage, then if the input is fixed (say 2Khz) then as the divisor is
> swept
> from 32 to 1 the
> amplitude AND frequency change. But, the amplitude drops off at higher
> frequency outputs
> since the counter is reset faster and faster.
> 
> Of course, if you fix the divide ratio and sweep the input, the amplitude
> of
> the sawtooth is *constant*
> at the divide ratio X 312mv.
> 
> Will add $15 to the cost of the module. Discuss!
>