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How to use simple circuit to converter +5V to -5V

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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.
 

See this link

/http://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm

Regards
Itp
 

Hi everybody

i think u can just use the LM7905 regulator to get the -5V as u use LM7805 to get the +5V

hope this helps u
bye
emmos
 

Sorry,My systerm only have +5V DC source,so I can not use 7905 to generate -5VDC.
 

Hi
Use CMOS Charge Pump Inverter if output current is not high,such as cat660,max660.

ynhe
 

i think u can just use the LM7905 regulator to get the -5V as u use LM7805 to get the +5V
Click to expand...
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.

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) or some 555 timer based homebrew switchmode.

hxxttp://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm
 

here a simple converter using icl7660
 

Assuming your main circuit is digital, there might be a clock there somewhere. Run it to a spare buffer, and connect a voltage doubler circuit to its output, for a negative voltage (two diodes and two capacitors). Depending on the load, the voltage might come to somewhat above 5 volts.
 

Use a timer 555 as a voltage inverter it will be very cheap at low powers
 

The best solutio is to use a charge pump ICL 7660 as described below. This integrated circuit costs less than US 1 thne isn't so expensive. If you want to do it by yourself you can use a digital CMOS buffer as 74HC245 oscillator and capacitors. You can also use a buck converter using a low cost pwm regulator as LM3524 from national.

nebisman
 

for such suggest,i think 555 is best method.
max660, ICL 7660 also are a good select,but the cost is expansiver than 555.

my project:
use this -5V for amp offset adjusting,and resolution is 300uV,so afraid ripple of 555 circuit will be too large for this application.
 
LC filter can not filter all noise,special for switching power supply.
 

Maxim and LT have some regulators which offer very low noise
 

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)
Click to expand...

I don't how big current you need, but maybe you can use max232 to have -15V and then use lm7905 to have -5V no the output :)

**broken link removed**
 

charge pump maybe have too large noise, anyone have another good method?
 

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