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Isolating 2 ckts from same pwr supply

E

Elephant

Jan 1, 1970
0
I want to use one 9vdc power supply to power two individual
circuits, but I want to isolate the two. In other words, the
two circuits have to act as though they are being powered from
seperate supplies, like two 9v batteries.

Can a diode arrangement be used for this?
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Elephant <[email protected]>
wrote (in said:
I want to use one 9vdc power supply to power two individual
circuits, but I want to isolate the two. In other words, the
two circuits have to act as though they are being powered from
seperate supplies, like two 9v batteries.

Can a diode arrangement be used for this?

Probably not. It depends on the exact circuit arrangements, why you
want/need to keep them 'isolated', and even what you mean by that.

If their ground/earth/zero volts lines can't be connected together, the
problem is almost certainly insoluble.
 
J

Joerg

Jan 1, 1970
0
With an isolating DC-DC converter this could probably be done.
Watch out for noise and other issues though.

Regards, Joerg.
 
K

Ken Smith

Jan 1, 1970
0
John Woodgate said:
If their ground/earth/zero volts lines can't be connected together, the
problem is almost certainly insoluble.

Exception:

Circuits like this can also be built:


9V --------------- To 9V CKT
!
!
/c
Va ---! NPN
\e
---------- To + side of other circuit
---------- To - side of other circuit
/e
Vb ----! PNP
\c
!
0V -------------------- To 9V CKT


The Va and Vb could come from a circuit that always keeps a 3.3V plus 2
diode drops between them but has them slide up and down in some way with
respect to the 9V.
 
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