* DC Current source
 * Max current > 1 A
 * Takes unfiltered DAC signal as input (differential)
 * LED power indicators
 * Heater power unregulated (but filtered?)
 * Regulators inside for the opamps


==== Related ELOGs ====
 1. [[https://nodus.ligo.caltech.edu:8081/40m/14113| Rana links to new design from Analog Devices]]
 1. [[https://nodus.ligo.caltech.edu:8081/40m/13759 | Kira's Overview sketch]]


==== TCR (Temperature Coefficient of Resistance) ====
 * The parts should be chosen so that the [[https://www.mouser.com/blog/dont-ignore-current-sense-resistor-tcr|TCR doesn't produce too much change in the heater current]].
 * Maybe its not much of a big deal since we have a temperature sensor for the feedback, but in some cases this circuit could be used as an open loop heater.
 * [[http://vishaypg.com/docs/63609/63609.pdf | Vishay Precision]] has some metal foil resistors with 0.2 ppm/C. The best from anyone else is 2 ppm/C. Most resistors are more like 20-200 ppm/C.