Issue with Constant Current Sink
While I cannot give you the same answer as jonk did, there is no need to. Your increasing voltage but: R1 is not a constant current source, therefore the voltage will rise at the Q1 collector and the MOSFET gate. That is why op-amps often have several stages of voltage and current regulation, to account for a wide range power supply yet draw the same idle current.

If R1 was a constant current source driven by a voltage regulator driven by a constant current source, then V+ could have a wide range, maybe 5 volts to 30 volts or so. The upper limit is the max ce voltage of Q1 or M1, whichever is lowest.

I will try to get in a schematic to show what I am writing about.

Ok, just what I wrote about. R1 is replaced with a constant current source of 650 uA. It is driven by a constant current sink of 2.65 mA. It has a 3.3 volt zener as a reference, so this circuit should keep the LED current mostly constant from 5 volts to 35 volts. The 2N39xx series has a 40 volt limit and is common and cheap.

Note that the 3.3 volt zener may need to be the 500 mW type to maintain 3.3 volts if V+ is only 5 volts or so.

To understand this more I suggest looking at schematics of op-amps to see the many stages they use for current regulation regardless of the supply voltage.







simulate this circuit &ndash; Schematic created using CircuitLab