From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 2026-02-17 06:40, piglet wrote:   
   > On 16/02/2026 22:08, Christopher Howard wrote:   
   >>>>>   
   >>>>> Circuit A is the basic squaring concept, relies on modern open-drain   
   >>>>> output comparators being pretty good switches to ground. Assumes you   
   >>>>> already have a source of sawtooth or triangle waves with defined zero   
   >>>>> and peak values in the system.   
   >>>>>   
   >>>   
   >>   
   >> I had a few follow questions, if you please, regarding the PWM squarer   
   >> (circuit A):   
   >>   
   >> - Does this circuit work in quadrant one only? If so, would any slight   
   >>    modification of the circuit allow for handling negative input voltages   
   >>    also?   
   >>   
   >> - Could you please tell me a little bit more about the low pass filter   
   >>    portion of the circuit? Does that particular configuration have a   
   >>    name?   
   >>   
   >   
   > The circuit I showed gives output of zero for negative inputs (the input   
   > would always be below even the lowest point of the ramp so the   
   > comparator output would always be low).   
   >   
   > To handle negative inputs precede it with a precision full wave   
   > rectifier aka absolute value circuit.   
   >   
   > Good place to look for examples:   
   >    
      
   It's not applicable here on account of the huge offset voltage and   
   one-quadrant operation, but FWIW you can make all sorts of integer and   
   fractional powers using glorified current mirrors.   
      
   Example:   
    Screen shot   
      
      
      
   The shunt resistor effectively nails one or more of the emitters still,   
   which produces the change in power law.   
      
   I'm using a square-root version of this one in a demo for a circuit   
   whose bandwidth wants to be quadratic in the supply voltage.  It's fine   
   inside a feedback loop, and may eventually get put in an ASIC.   
   (Unfortunately they don't make the CA3096 anymore.)   
      
   Cheers   
      
   Phil Hobbs   
      
   --   
   Dr Philip C D Hobbs   
   Principal Consultant   
   ElectroOptical Innovations LLC / Hobbs ElectroOptics   
   Optics, Electro-optics, Photonics, Analog Electronics   
   Briarcliff Manor NY 10510   
      
   http://electrooptical.net   
   http://hobbs-eo.com   
      
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