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   sci.electronics.design      Electronic circuit design      143,326 messages   

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   Message 142,616 of 143,326   
   john larkin to christopher@librehacker.com   
   Re: cheap analog square function?   
   09 Feb 26 16:47:32   
   
   From: jl@glen--canyon.com   
      
   On Mon, 09 Feb 2026 14:52:20 -0900, Christopher Howard   
    wrote:   
      
   >Hi, I was wondering what is the cheapest (and hopefully, simple to wire   
   >up) way to get an analog square function. I.e., input a voltage x, and   
   >get voltage x^2 out. Or x^2/10. Or some reasonable approximation of   
   >either of those.   
   >   
   >The standard trick is to feed the voltage into both inputs of a   
   >multiplier chip. But even those AD633 chips are tough to afford on my   
   >budget (around 20 USD each).   
      
   How accurate does it need to be? How fast?   
      
   There are some PWM tricks that are slow and cheap and use sort of a   
   lot of parts.   
      
   Log/antilog with diodes is fairly simple.   
      
   Square root gets nasty on the low end.   
      
      
   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)   

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