Richard Moore wrote: > Brooke, I read the patent with interest, and I cannot see how using > the LM399 and AD587 together represents an improvement over just > using a 399 and a chopper amp for the needed gain to get 10V (or > whatever) out. Geller's external adjustment R chain will suffer > tempco problems similar to a set of Rs used to gain-set the chopper, > and making the chopper an integrator with a long TC should help with > the 399's noise. You need a low pass filter with a well defined dc gain not an integrator. You can also average the outputs of several 399s to reduce the noise. However this requires a lot of 399s if one wants to reduce the noise by a large factor. The LTZ1000 is significantly quieter than an LM399. Its significantly cheaper to use a single LTZ1000 than an array of 399s with the same noise (using the same low pas filter). > Can anyone see where a further tempco improvement > from using the AD587might come from? > > Dick Moore > > Bruce
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