kim jone

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8 years, 10 months ago.

about power output

Hi there, I have a NUCLEO-F446RE. I saw there are GND, +5V, 3.3V output from the board. I need a -5V common ground with the board for my project. I wonder if there is a simple way to get a -5V out of the board? Thanks.

2 Answers

Sanjiv Bhatia
8 years, 10 months ago.

Can you share why you require the -5v rail ? How much current is required for this -5v rail ?

If you are needing to supply -5v with low current then consider a charge pump positive to negative converter like the TPS60400 or similar. If you require higher currents then you will need to consider an inverting buck / boost switching power supply. There are assorted assembled modules that will convert your +5v to -5v and are available through offshore suppliers that may be suitable for your project.

http://www.linear.com/product/LTC3261

Manel Marin
8 years, 10 months ago.

You can also design op amps to work with only one power supply by offset input, here there is a simple example: http://www.neatcircuits.com/op_amp.htm

Some modern op amp allow to work with rail voltages ( input equal to ground or positive and some even both ), that with the proper design, e.g.: differential amplifier, helps to avoid a negative power supply in most cases.

I prefer this approach, because a power converter not used can not fault.

I hope that helps!

Thanks Manel. OpAmp design is very far from my memory. As I understand from your statement and from the link, you are saying that using a voltage inverter (with opamp) is a better idea, do I understand it correctly? If so, I think it is simple enough for me to try.

posted by kim jone 06 Feb 2016

Yes and no. I only explain you that single power op amp dessign is possible.

For example, to amplify a small DC signal to use an inverter with capacitors is a bad idea, for that use I prefer a differential amplifier variant with one, variant with two or variant with three op am, with virtual ground and/or applying an offset to the inputs. Note that for DC amplifying you MUST take into account the input offset deviation and input offset drift of the choosen op amp, they will be also amplified affecting the output.

I hope I gave you a general picture of op amp single supply and DC amplifier design.

Here more examples (google "single supply op amp design techniques"): http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

posted by Manel Marin 07 Feb 2016