a first crystal node and a second crystal node that are for coupling across a crystal oscillator;

a plurality of current sources generating source currents that are relatively insensitive to changes in a power-supply voltage including an amplifier source current and an output source current;

a low-gain input stage having a gate on the first crystal node and outputting a buffered node buffered from the first crystal node;

a gain stage having a converter transistor that receives the buffered node on a gate and generates a varying current that varies with voltage variations of the first crystal node;

a current mirror that receives a current difference of the amplifier source current and the varying current, the current mirror generating a mirrored voltage by mirroring the current difference; and

an output stage that receives the output source current and the mirrored voltage, with an output transistor that has a gate driven by the mirrored voltage and is connected to the second crystal node,

whereby the varying current is mirrored by the current mirror to control driving of the second crystal node by the output stage.