Dual Higher Voltage Pwr Supply

[Arn C.]

I was wondering if I can use these two circuits together so I have a + and - Volts approx 16 volts using the below schematics.  If I can, could someone direct me how to do this?
Thanks!
Arn C.


http://www.geofex.com/circuits/+9_to_-9.htm

http://www.geofex.com/circuits/+9_to_33.htm

[Mike Burgundy]

The MAX1044 has a maximum input voltage of 10V, so switching polarity *after* boosting the voltage is out. You could boost voltage after the polarity switch, but you would need 3 chips (!)
The easy way is to use the 33V charge pump and install a resistive devider (as used in most regular opamp circuits) to split the voltage in half and create a virtual ground at 1/2V. Just make sure power consumption never goes beyond 2mA on the chip.

[WyldeSnake]

2mA is pretty weak though...I guess it's because I'm not too familiar with effects yet, but what are the typical ranges for current?

[Arn C.]

Mike writes

The MAX1044 has a maximum input voltage of 10V, so switching polarity *after* boosting the voltage is out. You could boost voltage after the polarity switch, but you would need 3 chips (!)

How can this be done?  I have a bunch of these chips....

Mike writes

The easy way is to use the 33V charge pump and install a resistive devider (as used in most regular opamp circuits) to split the voltage in half and create a virtual ground at 1/2V. Just make sure power consumption never goes beyond 2mA on the chip.

I am making a circuit that will require +16 volts vcc and -16vcc(for the ground pin) for the TL074 quad op amp.   I know how to make a resistive divider, and get 1/2 voltage for bias, Will this be okay for this circuit or should I run the V- to ground?  Or should I (You could boost voltage after the polarity switch, but you would need 3 chips (!) )?

Thanks!
Arn C.

[Mike Burgundy]

boost the voltage as per the schem. This gives you ground and +33V.
Build the circuit as you would with a battery, complete with devider. There's an article in the archives somewhere I believe (GEO?) on calculating devider R values.
If you boost after the voltage inversion, you stack two booster circuits on top of each other and make the bottom one believe that ground is actually +. Not sure how that would really work, plus one might get some weird behaviour due to coupling of the oscillators, etc. Think it's possible but I'd have to think on that and I don't have the time now...

[Mike Burgundy]

Oh, -16V is NOT ground - that sits between the two supply rails. Typo, right?

[Peter Snowberg]

Keep in mind that 2mA is a dinky amount of current and a TL074 will be very able to try to source or sink more than that (as will a TL072 for that matter). It's like powering a car with a hamster exercise wheel.

Sorry to be a wet sock, but I don't like little charge pumps for doing anything more than bias supplies on LCDs. They just get too problematical if you try to use them for V+/V- supplies. I've used them in data acquisition equipment, but never audio.

If you want to get a +/-16V supply for opamps, I would recommend a DC-DC converter that runs in the 100KHz range. These buggers can get expensive, but they work as intended. Look through the Mouser catalog for too many choices, but expect to pay between $10 and $20 for singles. You can always find the maker and get one or two samples too.

Take care,
-Peter

[WyldeSnake]

Couldn't you use the charge pump to split it down to +16/-16, and then use buffers to up the amount of current on each line?

[spongebob]

Couldn't you use the charge pump to split it down to +16/-16, and then use buffers to up the amount of current on each line?

This would work if you could power the buffer with a supply voltage >16V  :wink:

I'd try to find a small transformer with dual secondaries and make a simple PSU, it's not that difficult.

[zachary vex]

or use four nine-volt batteries.

[Arn C.]

Thank you for all the replies gents!   Not sure what avenue I will take yet.  I am doing a bit of experimenting on a new circuit, so I will try a few different things and see how it all works out.  
Thanks again for your suggestions!!!
Peace!
Arn C.