Help for circuit design about power supply

[CSharpdeveloper]

Hi everybody,
I need help about the circuit design for power supply (negative and positive voltage) and op-amp. I am using 12V battery and a great number of op-amps (symmetrical supply (+5V and -5V)). I want to supply all opamps with standard +5V and -5V. I dare say that i need use 7805 and 7905 (5V, -5V)voltage regulators. I designed a circuit but i can not supply with equal +5V and -5V. For 13 channel and, for each channel, i used 4 opamp, first opamp for differential input for sensor, second opamp for low-pass filter, third opamp for gain with 40db and fourth opamp for high-pass. So i need a great number of op-amps.
As a result, i need a Proteus design, 12 V battery, 7805 and 7905 negative and positive voltage regulators, a great number of opamps, 13 channel, for each channel, 4 op-amps, and positive (+5V) and negative (-5V) voltages for op-amp supply.
I used a voltage divider but the obtained voltages wasn't equal with +5V and -5V. When the opamp numbers increased, positive and negative voltage values are changing.
Thanks for help.

[temtronic]

Please read PIC101 !

This is NOT a Proteus website!! It's specifically for everyone using the CCS C compiler for PIC microcomputers.

From your question, I suggest you go to a PROTEUS website

That being said you'll never ,ever get opamps to operate reliably with 7805/7905 as the V++,V--.What you need is a 'tracking dual regulator'(ie: 1495 (?),been 20 years since I did them..).This type of regulator will keep the + and - outputs to within a millivolt of each other.
If you can't find one( try Google...), you can 'roll your own' using high quality 'rail to rail' opamps.

good luck !
hth
jay

[CSharpdeveloper]

Dear temtronic,
I have been used 18f2550 microcontroller and CCS C for this project. I have not a problem about CCS C and microcontroller in the project. The only problem in this project is about negative and positive supplies of op-amps. I think that maybe someone in the forum give an idea about the problem. I have been using low noise, rail to rail and high precision opamps. These opamps needs symmetrical supply (negative and positive). But the battery has positive voltage and ground. The sensor output is consist of negative and positive signals. For this reason, i need positive and negative supplies.
Thanks anyway.
Yours sincerely.

[newguy]

http://www.ti.com/ww/en/simple_switcher/index.html?DCMP=simple_switcher&HQS=switcher

[temtronic]

Please be aware that switching power supplies are very 'noisy', and need a proper filtering if your opamps are working with millivolt sensor values. Resolving 1 millivolt or less can be done, just be careful with board layout, bypass caps, etc.
Depending on the signal use the 'Olympic' averaging function or if enough time, sample 16 or 32 times.

hth
jay

[Ttelmah]

Generate one rail, and split it.

Look at the TLE2426.

Trying to generate two rails, is 'asking for trouble', unless you spend a lot of effort making your own precision tracking regulator for the second rail.

Best Wishes

[avatarengineer]

I understand the need for such things;
my company develops power converters and instrumentation.
If you need help, contact me directly;

regards,
Anthony Esposito, CEO
Avatar Engineering Corporation
7701 E. Gray Rd ste 101
Scottsdale, AZ 85260
(480) 269-1370 Main
www.avatarengineer.com
[email protected]
Skype "avatarengineer"