CRYSTAL OSCILLATOR

• US 20110037525A1
• Filed: 08/13/2010
• Published: 02/17/2011
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: LEE, Chao-Cheng
• Granted Patent: US 9,030,265 B2
• Time in Patent Office: Days
• US Class Current: 331/116.FE
• CPC Class Codes: G04F 5/06 using piezoelectric resonators
• CPC Class Codes: H03B 5/364 the amplifier comprising field effect transistors H03B5/366 takes precedence

Abstract

This invention discloses a crystal oscillator, in which by appropriately designing the gain of an amplifier to achieve high trans-conductance and low power consumption. This crystal oscillator includes a first pad, coupled to a first node of a crystal, for receiving a crystal oscillating signal outputted from the crystal; an amplifier, coupled to the first pad, for amplifying the crystal oscillating signal to generate an amplifying signal; an inverter, coupled to the amplifier, for inverting the amplifying signal; and a second pad, coupled to a second node of the crystal, for outputting an oscillating signal to the crystal.

Claims

1. A crystal oscillator, generates an output oscillating signal by a crystal, comprising:

a first pad and a second pad, coupled to two nodes of the crystal;

an amplifier, coupled to the first pad, for amplifying a crystal oscillating signal receiving form the first pad and generating an amplifying signal; and

an inverter, coupled to the amplifier, for inverting the amplifying signal and generating the output oscillating signal;

wherein, the amplifier has a first power consumption, the inverter has a second power consumption, the first power consumption is smaller than the second power consumption.

2. The crystal oscillator according to claim 1, wherein the amplifier is a single-to-double-ended amplifier.

3. The crystal oscillator according to claim 1, wherein the amplifier comprises:

a first transistor, having a first gate received the crystal oscillating signal, having a first source coupled to a first operating voltage;

a second transistor, having a second drain coupled to a first drain of the first transistor, having a second source coupled to a second operating voltage;

a third transistor, having a third gate coupled to a second gate of the second transistor, having a third source coupled to the second operating voltage; and

a fourth transistor, having a fourth drain coupled to the second drain of the second transistor, having a fourth source coupled to the first operating voltage;

wherein, the second and the third transistors form a current mirror circuit.

4. The crystal oscillator according to claim 3, wherein the first and the fourth transistors are implemented by NMOS transistors;

and, the second and the third transistors are implemented by PMOS transistors.

5. The crystal oscillator according to claim 3, wherein the second gate of the second transistor is used as a first output terminal of the amplifier, and outputs a first amplifying signal to the inverter;

and, a fourth gate of the fourth transistor is used as a second output terminal of the amplifier, and outputs a second amplifying signal to the inverter.

6. The crystal oscillator according to claim 5, wherein the inverter comprises:

a fifth transistor, having a fifth gate received the first amplifying signal, having a fifth source coupled to the second operating voltage, having a fifth drain to output the output oscillating signal; and

a sixth transistor, having a sixth gate received the second amplifying signal, having a sixth source coupled to the first operating voltage, having a sixth drain to output the output oscillating signal;

wherein, the fifth transistor is implemented by PMOS transistor; and

the sixth transistor is implemented by NMOS transistor.

7. The crystal oscillator circuit according to claim 1, wherein the inverter comprises a feedback resistance coupled between an input terminal and an output terminal of the inverter.

8. The crystal oscillator according to claim 1, wherein the inverter has a gain, the gain is between 20 and 100.

9. The crystal oscillator according to claim 1, wherein the first power consumption is substantially equal to 1/10 of the second power consumption.

10. The crystal oscillator according to claim 1, wherein the first power consumption is substantially equal to 1/100 of the second power consumption.