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

[mag]

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.

 

[ITP]

See this link

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

Regards
Itp

 

[emmos]

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

 

[mag]

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

 

[ynhe]

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

ynhe

 

[Ozonehole2k]

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

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

 

[leemarrow]

here a simple converter using icl7660

 

[neelandan]

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.

 

[rauol]

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

 

[nebisman]

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

 

[mag]

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.

 

[rauol]

try using LC filters

 

[alphi]

LC filter can not filter all noise,special for switching power supply.

 

[rauol]

Maxim and LT have some regulators which offer very low noise

 

[adi-niunio]

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)

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**

 

[mag]

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