New filter schematic

[Paul Perry]

At 03:19 PM 3/06/99 -0500, Michael Lloyd wrote:
>Chris (and others who could answer):
>
>I've seen some circuits using multiple "3080 type" OTAs that share a single
>current limit resistor (R12 in your design), some that use individual
>resistors per OTA and some that use no resistors at all! Is there anything
>magical going on that affects the decision of how to do it? 

I put one on each for 'safety'.
People might think that having separate resistors driven from a common source
would help even the current, but if you are driving from a constant current
source (which you must to get the stuff to work well at low cuirrents) I
wonder what is really going on? Because, who knows the input impedance
to the 3080 bias control really is? And, the crucial characteristics of the 3080
vary over a 2 to 1 range, AFAIK, which has implications for the ckt also.

paul perry melbourne australia