...but funnypvision said:Completely off-topic...
...but funnypvision said:Completely off-topic...
digital computers have trouble with infinity too... try to divide by zero....PRR said:> I have a feeling split rail supplies only really came about because of the need for dc vacuum tube amplifiers.
Operational amplifiers generally. Mechanical or thermonic.
The natural field of Operational Amplifiers is Real Numbers. Both sides of Zero. (And in practice something less than infinity; we do not have infinite grasp.)
Some problems appear to have only positive solutions. Gun-aiming, you want the shell to go toward the enemy not behind you on your own mess-hall. The altitude of an airplane should always be positive. However the partial products needed to compute error of angle and powder or rate of climb will often run negative. Windage may be east or west, climb may be up or down, which are +/- analogs naturally.
We could run a single +400V rail, define "+200V = Zero", subtract 200V from all our inputs and outputs. This is cumbersome, messy, and error-prone. It seemed to be (usually is) simpler to run bipolar rails (mechanical hangers or electronic power supplies).
NOON said:To get more specific about it, if I have an existing preamp board (based around a THAT 1512 preamp chip and THAT 1646 output driver) designed to work with a conventional linear +\-18V supply and I have a Meanwell LRS-35 36V power supply https://www.meanwell.com/productPdf.aspx?i=395 what is the general consensus on the best way of using them together?
I don't think that will work. LM317 is not designed to sink current.moamps said:The simplest solution IMO would be using LM317 reg for creating +18V from +36V and using it as reference (common, ground).
It will work, IMO. If the output current from LM317 is too small, it can be loaded with 390 ohms/1W resistor for example to ensure stability. In the attachment is a similar solution.squarewave said:I don't think that will work. LM317 is not designed to sink current.
As long as only relatively high impedance bias voltages are being used, then a simple virtual ground can be used. An op amp will make it stiffer if you have an extra one anyway.
"floating" is important if you want to make things simple.NOON said:It's a floating 36v supply and I'd prefer to treat the preamp circuit like a 'black box' with no modifications like biasing it to a halfway voltage, adding blocking caps etc.
Certainly. It may work somewhat, but any current unbalance between the positive and negative rail is going to be a problem. Indeed you need at least a big capacitor to decouple the rail.Simple answer is add a couple of resistors, one from each rail to circuit 0v then nail that point to chassis ground. I assume there is a more optimal answer,
That's why some precautions must be taken in order to ensure stability with a heavy capacitive load, which is not that hard to do actually.squarewave said:But again the power supply bypass caps might cause instability because, in the case of the VG op amp buffer at least, you would be connecting the output of the OA to the power supply rails through caps which is a dubious thing to do.
I don't get it. Since the output of the rail-splitter is connected to ground, what offset are you considering?Also, any offset from the op amp is going to be reflected on the outputs.
True. There is an offset but since everything is hanging on the output it's not an issue.abbey road d enfer said:I don't get it. Since the output of the rail-splitter is connected to ground, what offset are you considering?
PRR said:> I assume there is a more optimal answer, but most people seem to be as confused as me about it.
Me not confused. Sell the single supply and buy a dual supply.
Sorry if you do not like this answer.
Exactly; that's why I mentioned studying the old dbx160 (VU).JohnRoberts said:I am repeating myself, but there is a lot of older designs that used single supply, maybe research some old school designs.
abbey road d enfer said:Exactly; that's why I mentioned studying the old dbx160 (VU).
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