I tried making a -5V supply but after connecting the circuit as shown below and applying 8V DC at input terminal, 7905 ic was taking more current and power supply acting as constant current source. I didn't get the desired output. Can anyone tell what could have happened? and suggest any ideas if any to make -5V supply from 7905 ic.

 

Show photos of your implementation

 

How do you expect a positive voltage in to produce a negative voltage out? The LM79xx series parts don't work that way

 

Hi P,
How did you connect the INPUT,?
E

 

Hi P,
How did you connect the INPUT,?
E

Pin 1 - (Ground and -ve terminal of 2.2uF capacitor)
Pin 2(Input pin) - (+8V DC)
Pin 3(Output pin) - (-ve terminal of 1uF capacitor)

 

hi P,
The Input must be minus 8v. IE -8v and common/ground 0V
E

 

hi P,
The Input must be minus 8v. IE -8v and common/ground 0V
E

So if I connect ground terminal to +8V and Vin terminal to 0V it won't work?

 

Pay attention to the pinout of LM79xx negative voltage regulators.

 

So if I connect ground terminal to +8V and Vin terminal to 0V it won't work?

ONLY if the 8V power supply mentioned does not connect to anything else at all, but is floating. When you refer to a voltage as "0V", it seems to indicate it has that wire connected to a common rail. It should be the +8V is now "0V" and the 0V becomes "-8V".
So if this supply is used for anything else, like a +5V supply, then you need to find another.
Also, as shown in post #8, the -Ve regulators have different pin-outs than the +Ve versions. Also, the tab must be insulated from the gnd as it is the -Ve input, not 0V as is the case for the 7805 +Ve regs.

 

Two things:FIRST, BEWARE that the pin-out for the negative regulator IS DIFFERENT, and second, you still need the 0.1 mfd capacitors really close to the regulator to prevent oscillation, which will produce all kinds of strange results. I have experienced that early in my career, the warnings are valid.

 

So if I connect ground terminal to +8V and Vin terminal to 0V it won't work?

If you need to generate a negative supply line from a positive input, you need a different chip and a different architecture than a linear regulator.

For example this:
https://www.vishay.com/docs/76946/creatingnegativeoutputvoltage.pdf

or this:
https://www.ti.com/document-viewer/lit/html/SSZT970

 

By having capacitors in series between 2 outputs having opposite polarities allows
the center node between the 2 capacitors to be common.

 

If you need to generate a negative supply line from a positive input, you need a different chip and a different architecture than a linear regulator.

For example this:
https://www.vishay.com/docs/76946/creatingnegativeoutputvoltage.pdf

or this:
https://www.ti.com/document-viewer/lit/html/SSZT970

Thanks for sharing this.. I'll definitely try out this circuit!