A crystal oscillator may be configured to limit crystal drive level in the crystal oscillator by clamping via a diode-resistor branch, voltage applied to a drain pad of the crystal oscillator. The crystal oscillator may incorporate Pierce crystal oscillator based implementation. The crystal oscillator may comprise an on-chip main branch, comprising at least one transistor element; an on-chip drain branch connecting the main branch to a drain pad; an on-chip gate branch connecting the main branch to a gate pad. The diode-resistor branch may be connected to the drain branch, and may comprise at least one diode and at least one resistor element. The at least one diode and the at least one resistor element may be connected in series in the diode-resistor branch. The clamped voltage may be applied from an off-chip drain node, through the drain pad.