Simplest possible negative supply - Electronic Circuits Projects Diagrams Free

Pax Writer · 12th September 2007, 09:30 AM

Hello all

I'm building a portable sound amplifier circuit which is powered by a single 9V battery. However, the TL072s in the circuit need some sort of +/- supply. I was thinking about trying out a MAX232 or similar RS232 line driver, which makes +/- 10V unregulated power, but my question is:
Do you know of a better/simpler/cheaper/smaller (physically) solution to this problem?
The current I need will probably be in the tens of milliamps at most, so the demands on the supply aren't too great. Regulation would be nice, though.

I ask this question both because of ignorance, but also because the ingenuity of other people often surprises me.
I hope you can help.

**Nigel Goodwin** · 12th September 2007, 09:37 AM

Generate a split supply using two simple resistors, there are examples all other the net, and all over these forums - this will give you +/-4.5V.

eng1 · 12th September 2007, 10:17 AM

Quote:

Originally Posted by Pax Writer

I'm building a portable sound amplifier circuit which is powered by a single 9V battery. However, the TL072s in the circuit need some sort of +/- supply. I was thinking about trying out a MAX232 or similar RS232 line driver, which makes +/- 10V unregulated power, but my question is:
Do you know of a better/simpler/cheaper/smaller (physically) solution to this problem?
The current I need will probably be in the tens of milliamps at most, so the demands on the supply aren't too great. Regulation would be nice, though.

Maxim have charge pump DC-DC converters suitable for your application. The ICL7660 has been commonly used to generate a negative supply for an op-amp. It can deliver 10 ma max. http://datasheets.maxim-ic.com/en/ds...60-MAX1044.pdf

You'll find newer solutions at maxim-ic.com

Gayan Soyza · 12th September 2007, 10:43 AM

TL072 supports to single supply arrangement so you can directly give supply from battery.

eng1 · 12th September 2007, 10:47 AM

Pax Writer, what voltage swing do you expect at the output of the TL072?

audioguru · 12th September 2007, 01:01 PM

ANY opamp can be powered from a single supply.
An opamp's supply doesn't need to be regulated.

Here is an opamp that is biased at half the supply voltage and has input and output capacitor coupling so it can use a single supply:

Pax Writer · 12th September 2007, 10:10 PM

@eng1: Ehm, honestly I'm not quite sure. The TL072s in my circuit are only preamps, and so I don't expect a very big voltage swing. No more than 2-4 volts maybe.
The final stage will drive a set of headphones.

Pax Writer · 12th September 2007, 10:13 PM

@Audioguru: Thanks for the great illustration. I definately need to read more into the finer points of op amps. Can you shortly explain why the output capacitor couplings?

Hero999 · 12th September 2007, 10:34 PM

They are DC blocking capacitors or AC coupling capacitors; without them the output signal will have half the supply voltage DC superimposed on it.

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12th September 2007, 09:30 AM	(permalink)
Pax Writer	Simplest possible negative supply Hello all I'm building a portable sound amplifier circuit which is powered by a single 9V battery. However, the TL072s in the circuit need some sort of +/- supply. I was thinking about trying out a MAX232 or similar RS232 line driver, which makes +/- 10V unregulated power, but my question is: Do you know of a better/simpler/cheaper/smaller (physically) solution to this problem? The current I need will probably be in the tens of milliamps at most, so the demands on the supply aren't too great. Regulation would be nice, though. I ask this question both because of ignorance, but also because the ingenuity of other people often surprises me. I hope you can help.

12th September 2007, 09:37 AM	(permalink)
Nigel Goodwin	Generate a split supply using two simple resistors, there are examples all other the net, and all over these forums - this will give you +/-4.5V. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

12th September 2007, 10:43 AM	(permalink)
Gayan Soyza	TL072 supports to single supply arrangement so you can directly give supply from battery. __________________ Gayan My Website http://gsmicro.blogspot.com/

12th September 2007, 10:47 AM	(permalink)
eng1	Pax Writer, what voltage swing do you expect at the output of the TL072?

12th September 2007, 10:10 PM	(permalink)
Pax Writer	@eng1: Ehm, honestly I'm not quite sure. The TL072s in my circuit are only preamps, and so I don't expect a very big voltage swing. No more than 2-4 volts maybe. The final stage will drive a set of headphones.

12th September 2007, 10:13 PM	(permalink)
Pax Writer	@Audioguru: Thanks for the great illustration. I definately need to read more into the finer points of op amps. Can you shortly explain why the output capacitor couplings?

12th September 2007, 10:34 PM	(permalink)
Hero999	They are DC blocking capacitors or AC coupling capacitors; without them the output signal will have half the supply voltage DC superimposed on it. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.