Negative Reference Voltage

[nick_o]

Hey guys, i'm very new to electronics so please bear with me :)

I'm trying to use a DAC chip which is giving me all sorts of headaches.

At present I need to supply a reference voltage of -12v. How am I to source -12v?
The only way i can get my multimeter to read that is by swapping the positive and negative leads? Is this the right way to go?

Thanks very much for your help :)

Nick

[audioguru]

Hi Nick,
Welcome to our forum. ;D
There are a few simple ways to make a negative reference voltage. An ICL7660 takes a positive voltage and makes a negative voltage. A few Cmos inverters or a 555 oscillator can have a rectifier and filter cap added to do it.

I don't think DAC ICs require a negative reference voltage. Attach your schematic for us to see why.

[nick_o]

Hello audioguru how are you? Thankyou for your response.

It is perfect that you are an audio guru, because this is the exact application i eventually have in mind with all this DAC business :)

The DAC in question is just 8-Bits, i know this is less than ideal for audio - but you've got to start somewhere right?

This is the circuit I'm trying to setup at the moment:



To be honest i'm a little confused. From what i can gauge the reference voltage goes in at pin 3 & 13, and you get your analogue out at pin 4. Although my experiments so far don't seem to confirm this. Also all these different voltage inputs are confusing.

Any help you can give would be greatly appreciated. I managed to get some audio sampling (at shocking quality) with my own resistor ladder, although they weren't precision matched resistors so I suppose that wouldn't help. Also i only provided GND as a negative voltage so that mightn't help either might it as audio is bipolar is that right?

Also, this is the datasheet if that helps: http://www.dse.com.au/isroot/dse%5Csupport/Z6834.pdf

Thankyou very much for your help :)

[mvs sarma]

Hi,
In support of audio guru's opinion that you can work with one supply,  attaches find a application note URL

http://www.national.com/an/AN/AN-1525.pdf

this will enable you work with single voltage.

[nick_o]

Hey guys, thanks for your help.

Thanks for digging up that reference sarma, i'll definitely use it to test out this dac. This dual rail chip sure is a headache.

For audio needs i'll use the negative reference too.

Thanks guys.