Wilson current mirror

Addition of a cascode transistor to the simple current mirror increases the output impedance (immunity to output voltage variation) because the collector voltages of the lower pair are fixed. The cascode transistor doesn't need to be matched - but it helps.

h_FE		Min	Typ	Max
NPN	SSM2210P	300	605
NPN	BC184L	100
PNP	SSM2220P	80	165
PNP	BC214L	140		400

β_m	β_c	I_out I_prog	%
300	100	0.987	1.3
605	100	0.984	1.6
80	140	1.010	1.0
80	400	1.020	2.0
165	140	0.998	0.2
165	400	1.007	0.7
100	100	1.000	0.0

β_m = Current Gain (h_FE) of matched pair

β_c = Current Gain (h_FE) of cascode transistor