[continued from previous message]   
      
   >Bill will be along soon to tell us who designed what and how he did this or   
   that but we   
   >all know that anyway.   
   >   
   >I don't claim any credit for this circuit except for the Q1 Q2 circuit which   
   I arrived at   
   >by doing online research into how it might be implemented. AS3944 might be a   
   good   
   >choice for that circuit.   
   >(This won't stop Bill, for the nth time, pointing out how further refinements   
   were added   
   >but who cares.)   
   >   
   >I wanted to see whether it could be done without thermistors, opto devices,   
   lamps, FETs   
   >or similar devices. And also without large capacitors. After all if you   
   wanted to implement   
   >it all on a chip then you don't want those kinds of components in the circuit   
   if you can   
   >avoid them. And none of the FET based circuits I ever saw could match the   
   LTSpice   
   >performance of this circuit.   
   >   
      
   16 to 20-bit DACS are available. Given a sine lookup table in ram, one   
   could fine tune it for sub-PPM distortion. Or use a 16-bit DAC and sum   
   in another 16-bit DAC that nulls the distortion, even the distortion   
   of output amps or whatever.   
      
   The problem is how to measure the distortion to close the loop.   
      
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)