I have a labb supply with output single rail 0-30V.
Now I want to use the labb supply to fead dual supply circuits.
What I need is a supply splitter and so create a virtual ground.
To increase the current I want to use two paralleled OPA134.
Now if you look at my picture you see how I think it might work.
But I think I have to put in a couple of resistors when paralleling.
But I dont know where?
Now I want to use the labb supply to fead dual supply circuits.
What I need is a supply splitter and so create a virtual ground.
To increase the current I want to use two paralleled OPA134.
Now if you look at my picture you see how I think it might work.
But I think I have to put in a couple of resistors when paralleling.
But I dont know where?
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Offset differences will be minimal with FET opamps. 0.5 ohm would be good.
Even better (and I did this on my Farnell PSU) is to use a single opamp driving a complementary pair of transistors. Add current limiting in the normal way and you can get a small and compact virtual ground capable of sourcing or sinking a 100ma or so.
Even better (and I did this on my Farnell PSU) is to use a single opamp driving a complementary pair of transistors. Add current limiting in the normal way and you can get a small and compact virtual ground capable of sourcing or sinking a 100ma or so.
Thanks Mooly.
I have been looking at other op amps, too.
NE5534 is one - with comp cap it is unity gain stable.
OPA134 tells max +/-35mA is max.
Having one opamp driving a complementary pair, of course would give lots of current.
Such a transistor pair could be BD139/140 and give very good drive.
I have been looking at other op amps, too.
NE5534 is one - with comp cap it is unity gain stable.
OPA134 tells max +/-35mA is max.
Having one opamp driving a complementary pair, of course would give lots of current.
Such a transistor pair could be BD139/140 and give very good drive.
Something like the OPA134 or even TL071 is perfect. Low current consumption and no offset issues. There are dozens to choose from though although the 5534 wouldn't be my first choice tbh.
I added mine to the unused blue terminal and so I have a dual 3-0-3 to 15-0-15 variable supply. The lower limit is set by the opamp not working at low supply voltages. Its great, its always there when needed, and when you don't need it you just forget its there.
I added mine to the unused blue terminal and so I have a dual 3-0-3 to 15-0-15 variable supply. The lower limit is set by the opamp not working at low supply voltages. Its great, its always there when needed, and when you don't need it you just forget its there.
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Hi lineup
The thing to look out for is that the bench power supply is true floating type. If the PS is not floating then, your virtual ground will have a problem with the test equipment that is typical unbalanced and or ref to power ground.
The other thing I see it that I would add diode protection to the input and the outputs. Add bypass for the opamps.
Duke
The thing to look out for is that the bench power supply is true floating type. If the PS is not floating then, your virtual ground will have a problem with the test equipment that is typical unbalanced and or ref to power ground.
The other thing I see it that I would add diode protection to the input and the outputs. Add bypass for the opamps.
Duke
http://www.diyaudio.com/forums/full-range/249372-mini-dcaav-dayton-nd91.html#post4559002
Used to use a single BUF634 with 2 resistors.
But have now updated to a single OPA544 in unity gain for lower Zout.
Will do 2A with ease, with a suitable heat sink.
Also built extra two for the lab supplies.
Patrick
Used to use a single BUF634 with 2 resistors.
But have now updated to a single OPA544 in unity gain for lower Zout.
Will do 2A with ease, with a suitable heat sink.
Also built extra two for the lab supplies.
Patrick
First, what is 'the unused blue terminal'?
I have already looked at TLE4026. Too little current.
BUF634 is a very good option. But find it very expensive and is not at my regular shop.
OPA544 I also have looked at. But very hard to find here.
LM675 - would this not be an option?
Audio1Man ... what problem can this be?
Will not the virtual ground be the new ground point for everyhing?
I have already looked at TLE4026. Too little current.
BUF634 is a very good option. But find it very expensive and is not at my regular shop.
OPA544 I also have looked at. But very hard to find here.
LM675 - would this not be an option?
Audio1Man ... what problem can this be?
Will not the virtual ground be the new ground point for everyhing?
Best is to use a Buffer Op Amp, like BUF634, OPA633, LME49600.
Other power op amps can be unstable at unity gain.
But OPA544 looks to be stable at Unity Gain.
I can buy BUF634 or OPA544. OPA544 costs more money. But BUF634 is also expensive.
OPA633 I can not find here.
We also have the LT1010
Other power op amps can be unstable at unity gain.
But OPA544 looks to be stable at Unity Gain.
I can buy BUF634 or OPA544. OPA544 costs more money. But BUF634 is also expensive.
OPA633 I can not find here.
We also have the LT1010
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THis issue has been solved.
I am going to buy a dual power supply.
This can put out 2x30V 2x3A.
So I get automatically 60V with a ground in the middle.
Velleman LABPS23023
https://www.esr.co.uk/manuals/461-560.pdf
I am going to buy a dual power supply.
This can put out 2x30V 2x3A.
So I get automatically 60V with a ground in the middle.
Velleman LABPS23023
https://www.esr.co.uk/manuals/461-560.pdf
OK, let’s back up so we can see the forest and not the trees. Who needs to run the opamp bare foot? Add a NPN transistor to the opamp; connect the collector to +power of the opamp, base to output and emitter to – input. The circuit will then be 100x more current depending on the added transistor. I hope this may help.
Duke
Duke
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