Author Topic: Virtual ground circuit  (Read 8263 times)

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Offline soldar

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Re: Virtual ground circuit
« Reply #25 on: January 12, 2019, 09:10:55 am »
I can't find any information about a discrete audio amplifier being used as a rail splitter in the thread that you link- have I missed something?
No. I only mention that the discrete component audio amplifier I posted there can very easily be modified to make a rail splitter because basically it already is a rail splitter. That's all. And it could handle up to 60 volts or more which is its working voltage.

Besides which, are you really suggesting that you dedicate a whole discrete audio amplifier to generating a 0V rail- surely not.
I am not suggesting anything. I see all sorts of threads with people doing things I would never do but they have their reasons. People build with discrete components things you can get done by one IC. People are building circuits using tubes and old technology. People have fun doing whatever it suits them. I am just saying that audio amplifier is, basically, a rail splitter or voltage divider. Maybe that information or point of view is useful to somebody. Maybe someone would like to build a rail splitter with discrete components or just understand how they would work.
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Offline spec

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Re: Virtual ground circuit
« Reply #26 on: January 12, 2019, 10:03:02 am »
I can't find any information about a discrete audio amplifier being used as a rail splitter in the thread that you link- have I missed something?
No. I only mention that the discrete component audio amplifier I posted there can very easily be modified to make a rail splitter because basically it already is a rail splitter. That's all. And it could handle up to 60 volts or more which is its working voltage.

Besides which, are you really suggesting that you dedicate a whole discrete audio amplifier to generating a 0V rail- surely not.
I am not suggesting anything. I see all sorts of threads with people doing things I would never do but they have their reasons. People build with discrete components things you can get done by one IC. People are building circuits using tubes and old technology. People have fun doing whatever it suits them. I am just saying that audio amplifier is, basically, a rail splitter or voltage divider. Maybe that information or point of view is useful to somebody. Maybe someone would like to build a rail splitter with discrete components or just understand how they would work.
Thanks for reply soldar. I understand now. :)
 

Offline aheidTopic starter

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Re: Virtual ground circuit
« Reply #27 on: January 12, 2019, 05:42:03 pm »
I am dying to know- what is this PSU for? :)

I was thinking of making a transistor curve tracer, just as a fun learning project. I was inspired by https://www.instructables.com/id/Transistor-Curve-Tracer/ but primarily wanted more symmetric handling of N and P channel transistors, as well as ideally higher current capability.

As such I thought a split rail would make things much easier for me, and that got me searching for rail splitters.

Now, gotten side-tracked by virtual ground circuits I didn't get much further thinking about the actual tracer. The main idea was to use a push-pull stage controlled by an opamp (referenced by a DAC) to provide a controlled collector current.

Having thought a bit more about my goal I imagine I have two options that might be better than full-blown virtual split rails:
- use push-pull MOSFETs and a charge pump to provide a negative supply for the controlling opamp
- use push-pull BJTs, and another opamp to adjust for the offset created by Vce(sat) when trying to pull the collector low when testing P-channel transistors

Anyway, thanks again for all the replies, they were very helpful and informative.
 

Offline aheidTopic starter

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Re: Virtual ground circuit
« Reply #28 on: January 12, 2019, 06:03:27 pm »
I should add I was curious about the virtual ground circuit for possible use in future designs as well.
 

Offline soldar

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Re: Virtual ground circuit
« Reply #29 on: January 12, 2019, 06:04:51 pm »
I was thinking of making a transistor curve tracer
Yeah, that should not require much current so you could make a relatively simple rail splitter. OTOH I am not sure it is strictly necessary.
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Offline spec

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Re: Virtual ground circuit
« Reply #30 on: January 13, 2019, 08:33:08 am »
I should add I was curious about the virtual ground circuit for possible use in future designs as well.
Good luck with your future designs aheld.  :)

And if you do build a curve tracer with split supplies or anything else please let us know how it goes.
 

Offline aheidTopic starter

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Re: Virtual ground circuit
« Reply #31 on: January 14, 2019, 12:14:39 am »
Inspired by the posts in this thread I ordered a class AB and a D amplifier circuit from AliExpress, their designs looked very close to the reference implementation. Will see if I can modify them to become rail splitters :)

As mentioned I'm awaiting the 2.5V reference in order to make the circuit that started this thread, as well as a couple of switch-mode controllers. Will hopefully try to make an inverter out of them.

Anyway, will post back here with any findings.

And if you do build a curve tracer with split supplies or anything else please let us know how it goes.

Thanks, will do!
 


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