Adjustable regulated power supply circuit diagram with low output voltage

This circuit is suitable for application under the following conditions: the minimum output voltage Uamin>0.5V. The output voltage Ua is the sum of Ub and Ur, where Ur is the voltage stabilization value of the integrated voltage stabilizing circuit.

The formula for adjusting the output voltage is Ua=Ur.R2/4. The current in the adjusting branches R4 and R5 is about 1mA (when Ua≈0.5V). The resistor R should be selected so that Ur1 has a value of 1V when I1 is minimum in the equation I1=Ir+I2 to ensure that the operational amplifier has sufficient negative voltage. The selection of R2 and R3 values ​​depends on the value of R4+R5, which should allow a current of about 1mA to flow, that is, R2+R3=Ur/1mA.