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there is an exact formula in baker's book,from the exercise he did with hand calculation and spice simulation ,it is quite accurate,however,it is too complicated,you can turn to the book.another question: why do you need to calculate it ,why not see it in the spectre simulation
Because in fab foundry's PCM data, some use constant current method to measure Vth, some use gmax method. And i found the constant current (1uA) Vth has large difference with the Vth in model files and spectre simulation. However the gmax method Vth is close to the Vth in model files and spectre simulation. So i want to know why?
i doing mosfet char from long time , do u need practical metod , as we mostly use gmamx metod to measur vth of atransistor. keep vds=0.1 v (linear region )
sweep vgs =0- 5v @0.05v plot both gm and Id , from point of max. value of gm draw a tangent , the point of X-axis where this tangent touches x-axis is known as vt of mosfet.