The output of my differential ring oscillator is from 1.2-1.8V.
Could anyone help me on what level shifter should I use to transform output to 0-1.8V? Preferably low power one.
The supply voltage is 1.8V.
Since you don't give us ANY usable information, like frequency, or application, like is this an IC design or a discrete circuit, there's nothing we can do for you.
Since you don't give us ANY usable information, like frequency, or application, like is this an IC design or a discrete circuit, there's nothing we can do for you.
A single transistor is able to do the job. Try a PNP type. You can operate it in common emitter mode or common base mode. (Common emitter inverts signal polarity. Common base does not.)
Install resistors at all legs. Adjust values so that output ranges from 0V to supply V.
An inverter stage of +0.6Vgs NMOS and -0.6Vgs PMOS, with two diodes in series with the N-channel gate. 1.2V = ~0V at NMOS gate and P on. 1.8V at gates = P off and N on. Or with NPN and PNP pair.