Current shunt for Home Made DC Bench power supply

[dave_birdi]

Hi all,

I am currently in the process on designing a bench power supply (which I intend on doing a proper write-up of at some point in the future).

The initial design does not have scope for digital control as of yet (control is derived from a 10-turn pot feeding in to an LM338)

However for my initial specification the design does need to be able to sense current and output voltage. Output voltage can be sensed by a microcontroller easily enough with a potential divider (and can be fairly accurate as I intend on powering the microcontroller from a precision 5V source)

I have read up on the theory surrounding the use of a shunt resistor and an op-amp in an inverting amplifier configuration that supplies an output voltage from the op-amp which can be fed in to an ADC on microcontroller (an Atmel in this).

The output voltage from the op-amp can be used to infer the voltage drop against the shunt resistor and hence the current flowing through the circuit.

My design as it stands involves the rectification from a mains transformer (output 20 V RMS) to produce a D.C. output.

My question is:
How important is it that I have split supply when using an op-amp for the above purpose? I have seen some op-amps that are designed to be used in a single-supply basis but these seem comparatively expensive.

I have found this link to be quite useful:

http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf

[Fank1]

Just get a single supply op-amp.