Embodiments of the invention provide a low-power, high-gain amplifier for a crystal oscillator. In some embodiments, the oscillator amplifier circuit comprises two NMOS transistors stacked in series with a PMOS transistor. In various embodiments, each of the NMOS transistors is diode-connected through a resistor and has the input signal capacitively coupled onto its control terminal. The stacked amplifier raises the DC level of the amplified oscillatory signal and can support a substantial oscillation amplitude without clipping.