From: liz@poppyrecords.invalid.invalid   
      
   Phil Hobbs  wrote:   
      
   > Hi, all,   
   >   
   > I'm doing a high-accuracy version of the laser noise canceller   
   > .   
   >   
   > In particular, to get better cancellation accuracy, I want to get rid of   
   > the input offset voltages of a couple of op amps.   
   >   
   > One approach to this is to use a chopamp integrator to snoop the summing   
   > junction, and dork the noninverting input to force the summing junction   
   > to average 0.00000V.   
   >   
   > This is nice conceptually, but there are a couple of worries:   
   >   
   > 1. Chopamps kick out nasty switching spikes, which will have to be   
   > decoupled sufficiently well.   
   >   
   > 2. Weird-ass composite amplifiers always have weird settling behavior.   
   >   
   > I haven't done this lately, but I'm thinking of a TLV2333.   
   >   
   > Any wisdom?   
      
   At that level of accuracy, beware thermocouple effects.   
      
   If you are compensating a slow drift in offset, chop slowly and   
   sinusoidally, then the 'spikes' will matter less.   
      
      
   --   
   ~ Liz Tuddenham ~   
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