Slew limiter

[jc]

Why could get an externally compensatable or externally biased op-amp (I
forget if the 709 has both options or not, look at early miller-type
op-amps ?! (ie diff-pair, integrator and buffer trio) ... in such op-amps
when the diff-pair is rocked all the way to one side (out-of-lock state)
the ramping slew rate is given by the level of the current biasing the pair
and also the value of the integrating cap -> SR=Cc/Ipair (V/s) ... if you
get an externally compensated op-amp you can switch-in variable amounts of
capacitance (in decades of 1,2,5,10 ratios) ... this may require several
switches to get a continuous enough stepping action or you could switch in
only a few values for course setting and then have variable bias set the
Slew Rate continuously, or you might get away with a variable bias
arrangement ... if you wire your op-amp open loop as an inverting switch (+
to gnd - input and out open-loop) then you should get controlable ramping
sffects from a VCO circuit ... you may have to tinker more if you're
dealing with a single power supply source ...  in the case of a bipolar
supply you may put together a simple 2n3906/3904 OTA circuit with two
current mirrors and integrate into a cap directly - in this case variable
bias is easily implementable but you'll still need a buffer stage at the
output ...

jc    							www.lynx.bc.ca/~jc


>Which type (or manufacturer of )slew limiter (if any) can work in the
>audio range for e.g. slewing a square wave from an vco?
>
>Thanks
>
>Paul
>
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