I've been trying to develop a precision voltage reference for HV power supplies and I'm using B2 Spice for simulations and I found it's pretty darn accurate. I have pictured below a curcuit I simulated, which is the voltage reference amp contained in the UA723 regulator,and it matches real world results very good! I used general purpose BJTs and a J111 for the ccs, and the Vref and Noise output is spot on. which is 7.25VDC and a noise output of 2.5uV. the HV Vref curcuit I put togther has a lower noise figure of 150nV, which I was surprised!