TLE2426 Q's

[gotdabluz]

Think about trying out one of these rail splitters/virtual grounds on a op-amp based design . . . have a couple questions regarding it's use for those of you who may be familiar with this device.

1)  Since it is a virtual ground, does this mean that I can use this connection point as the basis for my ground bus?

2) If I am putting this across my V+ connection, do I need some kind of blocking diode between this and the rest of my V+ connections to prevent reverse current, or does the device provide this itself?

Perhaps I am just not getting the point onhow this thing is actuall supposed to be wired up . . .

. . . diagram anyone?

[Paul Perry (Frostwave)]

I strongly recommend looking at the data sheet, just search google for TLE2426. You will also find plenty of applications from eg Headwize.
THe unit can sink or source up to 20ma, so you don't need a diode on the output.

As to whether the output is considered 'ground' or not, tha tis a question for the circuit, and for philosophers. But if you decide to connect all teh grounds in you system to the mid Vcc output, think about what the power supply is doing.. if your power supply has one side connected to 'ground' already.. :shock:  :oops:

[gotdabluz]

Thanks,

I looked over the datasheet but I was still lost . . . no example implementaions . . . but then . . .

I did find a schem at

http://tangentsoft.net/elec/vgrounds.html

And now I am clear as day on how this thing is supposed to work . . . humbly, my assumptions were pretty skewed . . . but I learn't somethin' and thats cool with me!

[cd]

What circuit are you using this for?

[R.G.]

To the best of my understanding, the TI rail splitters act like, and in fact are an opamp chip with only the +power, -power, and output pins coming out.  The - input is internally connected to the output, and the + pin is internally connected to a pair of resistors that split the power supply in half.  So...

1) Since it is a virtual ground, does this mean that I can use this connection point as the basis for my ground bus?

Yes, you may, as long as you NEVER tie that virtual ground to a different power supply. In effect, that means that if you do tie your ground bus to the virtual ground, the circuits it's in must have their own isolated power supply, and neither + nor - may be connected to another effect. You can't do that and then daisy chain power supplies to this and other single supply effects.

2) If I am putting this across my V+ connection, do I need some kind of blocking diode between this and the rest of my V+ connections to prevent reverse current, or does the device provide this itself?

Unless I misread the spec, it does not do its own polarity protection. You'll still need protection diodes.

Perhaps I am just not getting the point onhow this thing is actuall supposed to be wired up . . .

+ pin to most positive power supply, - pin to most negative power pin. The output is halfway between them and  can source or sink current within the limits of the device spec. You are free to hook any ONE AND ONLY ONE of the pins to a ground or power supply (but not both) shared with another circuit.

[Ed Rembold]

I've messed with these things enough to form the opinion that they were not intended for "audio" use.

At least, how I was using them- to provide bias voltage.
I found them to be noisey, and prone to oscillating at high frequencies.

The noise and oscillation  could be somewhat eliminated by taking the output through a 50 ohm resistor and then a 47uf cap to ground. However, too big a cap, and the oscillation would start again.
YMMV.

Ed R.

[R.G.]

As I said, **exactly** the same behavior as an opamp follower.  

Most followers, including MOSFETs and bipolars will oscillate under too big a capacitive load.

That, by the way, is what the inductor/resistor in series with the output of most audio amps is for - to isolate capacitive loads.