Simple DIY DVM Voltage Reference

[ppppenguin]

I remember using a tradtional thermal RMS meter to standardise PAL subcarrier (4.43MHz) amplitude. You measured the result at 4.43MHz. Then you applied DC instead and adjusted to get the same reading. Tedious and prone to burnout. The 8920A uses a pair of resistive elements and a pair of transistors as temperature sensors, nicely matched on a single chip. Then a feedback network drives the temp of one resistor to match the other one. Thus non-linearity (and there's plenty of that) is cancelled out.