Negative voltage reference with LM317

Thread Starter

Blue_Electronx

Joined Jun 10, 2019
37
Hi

In the circuit below, if I feed the circuit with +30V, will Zener D3 force the reference of +30V supply to be -13V instead of 0V? This would be like a negative reference instead of a negative voltage, right? I'm confused because I don't believe I'm creating a negative voltage with this setup. Is this setup good to power low power dual supply op amps?

 

crutschow

Joined Mar 14, 2008
23,542
That circuit won't do anything.
A Zener does not generate a voltage and more than a resistor does. All it does is drop a voltage equal to its rating when current goes through it in the reverse direction (cathode to anode).
You need a source of negative voltage.

What is supplying the +30V?
 

Thread Starter

Blue_Electronx

Joined Jun 10, 2019
37
The 310V is floating and it splits that to get the negative voltage.
You have to use the complete circuit to get a negative voltage, not just part of the circuit as you originally posted (which is why the circuit was confusing).
So, this means the ground from the rectifier is originally floating? (if not connected to anode of the 13V zener)
 
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