Voltage regulator that sinks current

[shpavel]

Hi
I am lookin some solution for a circuit I am designing. I have 5 volt and I need to create adjustable low voltages in the output. Something below 1.2 volt and above 0.3. The problem is that I need the circuit to be able sink and source current (something in the range of 50 mA). I have looked the web but my knowledge in vr is limited. Where do I start? Can buck step down solution do the work? Can linear vr do it?

[Kalvin]

Op amp.

[shpavel]

The DDR termination ldo are usually not adjustable. The come with constant voltage.

[tszaboo]

If you take a voltage regulator, and add a resistor on the output, you get a voltage regulator that can source less current than the maximal, it will waste energy continuously, but it can also sink some current. For 0.3V, 50mA you need 5 Ohm. Maximum waste is 1.2V 5 Ohm = 300mW, not too bad.
Or an opamp.

[cjm]

Op amp.

+1

...although sourcing 50mA at 0.3V might be challenging unless you have a negative supply rail for the opamp. Some rail to rail ("RRIO") opamps might just work with just 0v-5V rails - e.g. OPA340, AD8531 or similar.