-5v supply

[Data888]

Ok, another question. I have a +9v DC power supply, and I'm using a 7805
to get +5v for the circuit. But I need -5v as well, and I can't seem to
find anything to create that. The 7905 needs a -ve input voltage, and I
don't have one to give it. A few people have suggested other
semiconductors, but the electronics places near me don't carry them. So
any suggestions?

Nick

 

[Costas Vlachos]

Ok, another question. I have a +9v DC power supply, and I'm using a 7805
to get +5v for the circuit. But I need -5v as well, and I can't seem to
find anything to create that. The 7905 needs a -ve input voltage, and I
don't have one to give it. A few people have suggested other
semiconductors, but the electronics places near me don't carry them. So
any suggestions?

Nick

There are chips that can generate a negative voltage from a positive supply.
If your demand for current is not too high for the negative rail, you can
try the ICL7660S, or the even better LTC1046. These can generate -5V from
+5V with only two external capacitors. This is not a regulated output
though, and can supply up to 50mA of current. Very handy for op-amp
circuits.

cheers,
Costas

 

[Rich Webb]

Ok, another question. I have a +9v DC power supply, and I'm using a 7805
to get +5v for the circuit. But I need -5v as well, and I can't seem to
find anything to create that. The 7905 needs a -ve input voltage, and I
don't have one to give it. A few people have suggested other
semiconductors, but the electronics places near me don't carry them. So
any suggestions?

Hobby or production? If it's a home-brew project, MPJA has surplus
+5 / -5 DC-DC modules for a buck (no pun intended) in quantity 1.
Go to www.mpja.com and look for part number 2308 PS.