Single supply vs bipolar - Page 1
Forum section: electronics / beginners

author: axemaster
author_rank: Contributor
timestamp: January 07, 2023, 08:21:21 pm
content: Open ended question - does anyone really use bipolar power supplies? I always just design everything single-supply. Bipolar circuits seem cumbersome, both in the power supply design and also when you need to interface the analog-digital circuits to each other...Sorry if this is a super general question. I'm just curious what people think.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: January 07, 2023, 08:33:34 pm
content: Yes. Bipolar supplies are alive and well. What are you designing for? Audio, guitar effects will be OK with rail splitting and using the split as reference. When it gets to precision analog, like measurements and data acquisition, or high frequency the low impedance reference is more important than the convenience of a single supply.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 07, 2023, 10:00:34 pm
content: Sure. Even in cases where you could technically get away with single supply, it may be easier to just go with a split supply, especially if you need the voltage swing anyway. i.e., a +/- 5V analog system is often easier to deal with -- and interface with single supply digital electronics -- than a 10V single supply.These days, adding a negative supply is trivial whenever you actually need it. The main reason to avoid it is just he cost and PCB area, so yeah high volume consumer audio electronics will go to the slight extra design effort to avoid the negative supply, especially since they are mostly using highly integrated chips which avoid negative rails anyway.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 07, 2023, 10:14:51 pm
content: I do use bipolar perhaps I don't know better. I don't know how to make an OP amp works with single supply that can output both postitive and negative.

author: bdunham7
author_rank: Super Contributor
timestamp: January 07, 2023, 10:23:05 pm
content: Valid reasons to use single-supply include devices designed for (single) battery operation, very inexpensive low-performance things and applications that just don't need a bipolar or zero output at all. That covers a lot of ground. But where it is appropriate, incorporating a negative supply rail is usually trivially easy, so I can't see going to any great effort to avoid it.

author: TimFox
author_rank: Super Contributor
timestamp: January 07, 2023, 10:30:24 pm
content: I started my op-amp usage in the 1970s, when everything used a bipolar power supply and no op amps could swing near the negative rail.I still find it handy (although not necessarily with balanced supply voltages) to allow a signal ground node or layer that does not carry ripply DC current, to reduce noise problems.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 08, 2023, 07:26:31 am
content: Single supply circuits very commonly seen in battery powered circuits. Biasing arangements may add extra noise in your circuit.The precsion of the rail splitter and its tempco (generally awful on both counts) directly affects the circuits local reference voltage.A source of DC error that will appear on the output.Rail splitter ics are pretty good; a precsion of a few % and 30ppm/'C. A lot better than your typical reisistor ref generator buffered or not.Single supply circuits and low voltage opamps have become more common because of micro systems that just have a 3.3 or 5V rail available.Powering from your micro keeps your ADC safe(er) from over voltage. The opamp might die but your ADC wil probably survive.If you are making a precsion DC or a DC coupled circuit then dual rails make things far les complcated and you'll get much better performance.A single rail powered opamp can never truly swing its output to ground. Don't trust in the "Rail to Rail" hype! BTW rail to rail opamps nearly always have lower specs than their dual supply cousins. Often you need the wide swing from + to - . Impossible with single supply. If I have dual rails, even if they are not equal, I use them. eg -12V and +5V.The input common mode range is a function of the +rail. That can cramp your style.