Hi Jay_Diddy_B,
I fully understand fixed negative output. I don't understand Adjustable output. How can control FB votage by collector current? But It works in simulation.
This connection isn't for me, becouse i have negative control votage on senese resistor. It is from -11V to 0V.
The voltage from the FB to the GND pin is equal to 1.25V when the circuit is in regulation. The current in R1 = 1.25/20k = 62.5 uA.
Without Q1, the same 62.5uA flows in R2. The voltage across R2 = 62.5 uA x 150k
= 9.375V
The output voltage equals 9.375V + 1.25V = 10.625V
Q1 is connected in common base. Ic = Ie - Ib, Ib is small and we can consider Ic = Ie.
Ie = (V2 - 0.65V) / R3
The current Ic reduces the current in R2 to maintain equilibrium.
Vout = 1.25 + 150k
( 62.5uA - ((V2 -0.65)/R3))
What is the desired output voltage?
What is the control signal that you have?
Is the control signal referenced to ground or Vout?
Jay_Diddy_B