FET Parameters - Matching

[ronzeman]

If one uses beta to match bipolar transistors, what parameters are useful to match FETs. In particular I'm looking to match the Q1,2,3,4 for the input stage of a Hafler 9180 amp. What parameters? What percentages? ?? FYI devices are 2SK163 and 2SJ74

 

[h_a]

Match VGS at identical currents, that will do. If you want to improve that, use fets from the same batch.

Have fun, Hannes