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

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mag

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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.
 

ITP

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See this link

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

Regards
Itp
 

emmos

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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

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

ynhe

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

ynhe
 

Ozonehole2k

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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

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here a simple converter using icl7660
 

neelandan

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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

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

nebisman

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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

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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.
 

alphi

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

rauol

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Maxim and LT have some regulators which offer very low noise
 

adi-niunio

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mag

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

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