5A constant current/ constant voltage using LM350
PNP when Vbe=0.66V the current thru LDO is 0.66V/33 Ohm = 20mA.   


Above this load the PNP bypasses the LDO as a current source   
the LDO pulls up enough to regulate the voltage as the load decides how much current it needs.

R3 senses PNP current and the voltage rise is amplified thru the inverting input with gain via the pot, R2 with negative feedback to reduce the voltage drive using the LDO Vref 
the voltage reference, Vref is the Vou-Vadj on the LDO used by the Vadj pot to Vin-   
C5 adds a low frequency pole to reduce the 2nd order effects of the feedback loop and loss of phase margin towards loop stability
since Vref = 1.25 , when that is reduced by the conduction of D3,D1  it increases the LDO output voltage the same way a resistor divider does by sensing the output voltage with a resistor ratio.  Except the diodes here work as switches with the high open loop gain behind them regulated by the two pots.
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