From: user@example.net   
      
   On 2/10/2026 12:50 AM, Jan Panteltje wrote:   
   >> 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).   
   >   
   > For AC signals I wonder if you use a cheap analog volume control chip   
   > and put the signal on both the gain control and the signal input.   
   > Have not tried it though.   
   >   
      
   A pretty low parts count squarer is this old chestnut from EDN:   
      
      
      
   The ends of Vcontrol and V_in are both approximately at virtual ground,   
   so use equal-value resistors to make a current divider and drive them   
   with the voltage you want to square.   
      
   It's only one quadrant but it's decently fast and accurate and doesn't   
   need AC coupling, and even if you have to take the abs I think it's   
   still cheaper and way less fiddly than trying to roll your own   
   logger/antilogger.   
      
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