Comparing Constant Current Circuits (to sort/verify the LED-s with)

▼Fast/Simple/Robust/Trivial Op-Amp + BJT Setup▼
→ apx. 16mA ±30µA(0.2%)

[fig.1]

▼Complex/Trivial Op-Amp + BJT Setup▼
 → apx. 18mA ±24µA(0.1%)

[fig.2]

▼Simple/Experimental BJT Setup ( !? the Best ?! )▼
→ apx. 18mA ±60nA(0.0003%) 

[fig.3]

▼Full/Trivial BJT + N-jFet Setup ( also better than any op-amp variant ??? )▼
→ apx. 18mA ±300nA(0.002%) 

[fig.4]

▼Complex/Experimental Op-Amp + MOS-Fet Setup▼
(likely worse than it's BJT alternate -- the 2-nd ↑↑ fig. )
→ apx. 18mA ±120µA(0.7%) 

[fig.5]

▼Trying to get it right here▼
-- it seems that the op-amps should be fed from the separate supplies or otherwise the PSRR won't recover the precision reached at reference voltages
→ apx. 18mA ±48µA(0.3%) 

[fig.6]

((the work is in progress ...))

▼If you are stupid then knowing the right Op-Amp-s could save your day▼
(the node "SE" had the greatest error although the node "a0" has the least ??? -- about LT1012A)
→ apx. 18mA ±10µA(0.06%)

[fig.7]

-------- Update 2017.12.24 ::

▼a conditional opposite to "If you are stupid then knowing the right Op-Amp-s could save your day"▼

→ apx. 18mA ±7µA(0.04%)

 [fig.8.1]

a "Russian LM308" **

 [fig.8.2]

** it's nearest LT's substitute (so far)

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[Eop]