increase the output voltage of regulator

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Hi i want to clear some points regarding regulators.

I want to increase the voltage of a regulator (LM7824) from 24v to 40V. My input voltage is 48v.
I want to use the circuit which i upload.
I want to know how this regulator will work as its ground pin is not connected to the GROUND but connected with a resistor.
Will the output regulated or not?
If we use this regulator normally then we have a range of input between 30 to 40v, If i use regulator in this scenario then what will be the range of input as the ground is not connected direcly.
guys clear me if i am wrong.
 

The output voltage is internally set at 24V measured from the GND pin to the VO pin. Your circuit will work but because the GND pin is no longer an absolute reference you will get poorer regulation. A better solution would be to lift the GND pin up from 0V to a regulated 16V, that will give a fully regulated 40V out. Try connecting a 16V Zener diode from the GND pin to 0V with the cathode end toward the regulator. Also connect a capacitor (10uF) across the Zener and add a resistor from the GND pin to the incoming 48V to set a fixed current of around 1mA through the Zener. That will help to keep it's operating voltage stable.

Brian.
 

Just cut the grounded terminal of R2 and connect it to the cathode of a 16 V zener diode and connect the anode to the ground.
 

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