hi,

is it possible to produce a (-) negative voltage given a +12V supply?

if so, what kind of circuit would produce such?

thanks...

 

There are various ways, all fairly similar, either charge pumps or switchmode power supplies. Basically you need to generate an AC signal and then rectify it to give a negative voltage.

A lot depends on the current you require, for a low current requirement it should be quite simple - although with a charge pump you will always end up with a little less than -12V.

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Its siple svitch plus and minus.

12V = 0V
0V = -12V

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Il give you shocking experience.

 

heres 2 simple ways: use an op amp as an invertor or use a 7912 which is a -12 regulator

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An opamp wont work because it needs a negative voltage on it's negative supply pin. and the 7912 needs a negetive input in the first place.

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couldn't you just use a potential divider? - he didn't say he needed -12v, just a negative supply.

 

such a divider only works if the load on both the negative and the positive side is the same. If one side has a bigger load voltage will 'tilt' to the other direction

 

hi my frend
u can check the web site of analog devices electronics company
http://www.analog.com/

 

hi my frend
u can check the web site of analog devices electronics company
http://www.analog.com/ :P

 

The following circuit will work if you need 100Ma or less. The output voltage will be negative and will be approximately up to 1.1 volts less
than the input. There are two versions of the IC that I am aware of
LT1054CP by Texas Instruments, and LT1054CN8 by Linear Technology,
both available from Digikey.

Attached Images

lt1054cp.jpg (10.2 KB, 745 views)

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What neg voltage ? what current??

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gerty

 

For your info: An ICL7660 is a Direct Replacement for the LT1054 and Costs only 1/3 the Price.

Gary

 

I think you have it wrong.
The ICL7660 maximum input voltage for the regular versions is 10V while the A versions it is 12 Volts. Whereas the LT1054 has a maximum input voltage of 15V.

__________________
The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
Show me a different way. I have an open mind.

 

Here are the Specs:
ICL7660CPA is rated at 10.5 volts, ICL7660ACPA is rated at 13 volts, ICL7662CPA is rated at 22 volts And the LT1054-CN8 is rated at 15 Volts.

However, In tests I did with Various Batches of the ICL7660CPA, (with it claimed rating of 10.5 volts) It Works Perfectly OK with voltages up to "AT LEAST 16 Volts".

In Addition, I have a Metal Detector Project on my website that runs on a 12 Volt Sealed Lead Acid Battery, However, it Typically delivers 14.5 volts at a full charge. I have used this ICL7660CPA on well over 100 of these units, WITHOUT ANY FAILURES in over a year.

I believe all these chips are close to being identical, if not identical. Its more how they want to spec them for a particular price and application.

Reminds me of FLEA Powder for Cats and Dogs. They sell Both, But Both are Identical except for the label. However most persons have both will buy both. A Cheap way to increase Sales.

Try it Yourself, It is Much Cheaper to buy.
Take care.........Gary

 

Chemelec, you are correct about the specifications of the ICL7660CPA, the ICL7660ACPA, and the ICL7662CPA. So for a 12 volt circuit I would
still choose the ICL7660ACPA and the ICL7662CPA. I would hesitate to
use the ICL7660CPA in an application that exceeded the manufacture's specifications. That's my opinion anyway. Thanks for proving I was wrong about the ICL7660 series of voltage pumps.

__________________
The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
Show me a different way. I have an open mind.