Crystal oscillator

A crystal oscillator, comprising:

• a voltage stabilizing unit, a transconductance unit, a feedback resistor, a crystal resonator and at least two ground capacitors, wherein
• the voltage stabilizing unit comprises:
• a current source, M first branch circuits and M switches wherein
• M is an integer larger than 1, the first branch circuits are connected to each other in parallel and each of the first branch circuits is controlled by one of the switches respectively;
• each of the first branch circuit comprises a P-type Metal-Oxide Semiconductor (PMOS) and an N-type Metal-Oxide Semiconductor (NMOS) successively connected in series,;
• in each of the first branch circuit, the PMOS has its gate connected to a gate of the NMOS, the PMOS has its drain connected to a drain of the NMOS, the PMOS has its gate connected to the drain of the NMOS, and the NMOS has its source connected to ground;
• the transconductance unit comprises a second branch circuit, wherein the second branch circuit comprises a PMOS and an NMOS successively connected in series;
• in the second branch circuit, the PMOS has its drain connected to a drain of the NMOS, the PMOS has its gate connected to a gate of the NMOS, the PMOS in the second branch circuit has its source connected to a voltage output of the voltage stabilizing unit;
• the PMOS and the NMOS in the second branch circuit have their gates both connected to an input of the crystal resonator, and the PMOS and the NMOS in the second branch circuit have their drains both connected to an output of the crystal resonator;
• the PMOS and the NMOS in the second branch circuit have their gates both connected to one end of the feedback resistor, and the PMOS and the NMOS in the second branch circuit have their drains both connected to another end of the feedback resistor;
• and
• the at least two ground capacitors are connected to two ends of the crystal resonator respectively and are connected to ground.