Hi.
I made an addition to your scheme. This is the calculation of dH/dT by a separate, controlled current source with RC. The resulting value is used to calculate delta. I made a netlist and used it to calculate Qspice. I had to replace the parameter k with k0, because in Qspice k is the Boltzmann constant. At tau=10ns, the counting time was 2.2 seconds. And everything was fine.
