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My systerm all are +5V supply,But now have a amp circuit need -5V+-10%---10mA supply,how can I use a simple circuit to converter +5V to -5V.the special charge pump chip all are expensive,I only need a simple circuit.
LM7905 is yet another linear regulator. You still need a negative voltage to start with. Also, note the voltage drop of these device is not insignificant. In general, use a +7V unregulated supply if you are going to make +5V regulated with 7805; -7V unregulated to make -5V regulated.i think u can just use the LM7905 regulator to get the -5V as u use LM7805 to get the +5V
Ozonehole2k said:There are switchmode power supply ICs that handles the conversion. You can also try more common ICs like MAX232 (yes, the level converter for serial port, 0-5V in => +/- 15V out)