Hi all,
I am going to make +5v regulated DC power supply using LM7805 and 9V battery.Which company's battery will give better life time?Also I want to know whether it is possible to obtain -5V DC supply using LM7905 using the same battery?Or negative volted battery is compulsory to obtain -5v using LM7905?
Thanks in Advance.
Oh dear! 
Hi,
No...its.
Oh dear! 
Oh dear!
What is your electronics, programming, arduino, hardware experience?
A 9V battery that is used in a smoke detector is not going to provide the current for any of the arduino controllers for any reasonable length of time.
I am going to make +5v regulated DC power supply using LM7805 and 9V battery.Which company's battery will give better life time?Also I want to know whether it is possible to obtain -5V DC supply using LM7905 using the same battery?Or negative volted battery is compulsory to obtain -5v using LM7905?
I suggest you google... power supply tutorial
Tom...... 
Also I want to know whether it is possible to obtain -5V DC supply using LM7905 using the same battery?Or negative volted battery is compulsory to obtain -5v using LM7905?
You'd need a 2nd battery wired in the opposite direction.
Or, you can get a DC-DC (DC-to-DC) converter that can convert +9V to -5V. i.e. The output of an isolated DC-DC converter can be wired either way, just like a battery can be wired either way.
Sometimes two batteries are used but A DC-DC converter is the most common solution. If there are multiple batters in something, usually it's to get more voltage.
Another common solution is to design the circuit so it can run from a single supply.
Battery life is specified as mAH (milliamp hours) or Ah (amp-hours for bigger batteries). You might have to look at the manufacturer's datasheet, because it's not always listed on the package. I found [u]this[/u] for a particular Duracell 9V battery. It shows 0.58Ah (or 580 mAh). That means it should last 1 hour at 580mA, or 10 hours at 58ma, etc.
You'll need to check this but I believe mAh "life' is determined as 80% of the battery's rated voltage. That would be 7.2V for a 9V battery, and that is about the point where your 7805/7905 will drop-out of regulation.
Note that linear regulators (like the 7805 & 7905) are inefficient. With 9V in, you are "dropping" 4V across the regulator with 5V into the load. Both devices carry the same current, so you are wasting almost the same amount of power heating the regulator as you are powering your circuit. That means about half of your battery life is used-up heating the voltage regulator. (Power in Watts is calculated as Voltage X Current.)
Thank you all for the replies.
Actually I am going to use this regulator outputs for giving power supply for the amplifier circuit and the op amp used in the circuit not for the arduino.
I need a power supply which is small in size and better life time.That's why I am searching for power supply(+5V and -5v) which can be created from a single battery.
Hi,
How much power is the amplifier?
Do you have a circuit diagram of the amplifier?
Tom...
bisni:
That's why I am searching for power supply(+5V and -5v) which can be created from a single battery.
Not possible using the common definition for battery. (A single object.)
The true, (or original at least), definition, however, is a 'battery' of cells. If you make a battery of cells, connected in series, you can draw out a centre-tap for the 0V rail, then take the top and bottom rails as inputs to your 7805 and 7905. (That's still a single 'battery'. )
You'd need a total, (minimum), of about 14V though. 
And ........ Oh dear!.
I am using dual supply Op amp which needed +5 v and -5V.
@OLD STEVE
When I looked for the designin the internet its showing -ve dc inputvoltage needed for LM7905 and positive input needed for the LM7805. So it will make the powersupply section's size bigger.That's why I asked like that.
Tell us what you want to do.
Maybe you don't even need a dual rail opamp.
Leo..
I've used these in the past:
or
You need to feed it a regulated 5v supply, and it generates the +/- 5v you need for the Op-Amp. As long as you don't need more than 100mA, they work very well.
Ian.
@ian332isport
Bias current needed for my op-amp is in nA range.
The bias current is irrelevant to this discussion.
We are talking about the supply current.