Dual voltage regulator +5V & -5V

[NicholasTok]

lm7905 input

Hi

I have a small problem with my below schematic because I could not get 5V as I keep getting +2V to -2V.

I am using a +9V battery

If I was to use LM7805 and LM7905 can I use +9V input to get both a + & - 5V output?

I welcome to hear your suggestion

Regard,
Nicholas Tok

 

[asdfgh888]

lm7905 input range

To use LM7905, you need a negative voltage source. A 555 configured as an inverter can provide a low current negative voltage source.

 

[NicholasTok]

lm7905 regulator circuit

To use LM7905, you need a negative voltage source. A 555 configured as an inverter can provide a low current negative voltage source.

hi asdfgh888,

after looking into the datesheet of LM7805 and LM7905, in order to generate the + and - 5V my input range is 7V ~ 9V if i was to use a 9V battery. comparing to the circuit i am showing it has an input range from 6V to 9V. unless there is other components which allow a range from 6V ~ 9V

Regards,
Nicholas Tok

 

[oddbudman]

How much current do you require at +5 and -5v?

 

[NicholasTok]

How much current do you require at +5 and -5v?

hi oddbudman,

around 1mA

regard,
Nicholas Tok

Added after 1 minutes:

i came across this dual voltage regulator circuit using LM317 & LM337, can anyone help me see what is the input range like?

 

[FANT]

if it is just 1 mA, why don't you use two zener witha 7660 IC ?
If you have also a RS232 driver, you will find on it the voltages needed, jus put two regulators around it ( for more info see the data sheet of MAX232 from maxim ).

here the link:

**broken link removed**

You can get + 10 V at pin 2 and -10 V at pin 6; overall you can have directly the + 5 V from the battery with a 7805, and then the - 5 V from a 7905 with the input connected to the 6 pin of MAX 232

Mandi

 

[NicholasTok]

I have understand that dual voltage regulator LM317 & LM337 the Vin range is Vin - Vout = 5V

Which means in order to get a stable 5V output, my min Vin must be Vin - 5V = 5V
Vin = 10V

so the Vin must be equal or more than 10V to have a stable 5V...