OSCILLATOR CIRCUIT, DEVICE, AND METHOD

• US 20200136556A1
• Filed: 12/31/2019
• Published: 04/30/2020
• Est. Priority Date: 06/29/2018
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: LIN, Chi-Hsien
• Granted Patent: US 10,992,262 B2
• Time in Patent Office: Days
• CPC Class Codes: H03B 1/04 Reducing undesired oscillations, e.g. harmonics
• CPC Class Codes: H03B 2200/0034 including a buffer amplifier
• CPC Class Codes: H03B 2200/009 Reduction of phase noise
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1206 using multiple transistors for amplification
• CPC Class Codes: H03B 5/1212 the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1253 the transistors being field-effect transistors
• CPC Class Codes: H03B 5/1296 the feedback circuit comprising a transformer
• CPC Class Codes: H03H 7/0161 Bandpass filters H03H7/12 takes precedence

Abstract

A voltage-controlled oscillator (VCO) includes a first transistor cross-coupled with a second transistor, and a transformer-coupled band-pass filter (BPF) including a first transformer and a second transformer. The first transformer is configured to control a gate and a drain terminal of the first transistor, and the second transformer is configured to control a gate and a drain terminal of the second transistor.

Claims

1. A voltage-controlled oscillator (VCO) comprising:

a first transistor cross-coupled with a second transistor; and

a transformer-coupled band-pass filter (BPF) comprising a first transformer and a second transformer,

wherein

the first transformer is configured to control a gate and a drain terminal of the first transistor, and

the second transformer is configured to control a gate and a drain terminal of the second transistor.

2. The VCO of claim 1, wherein

the first transformer comprises a first winding coupled between a power supply source and the drain terminal of the first transistor, and a second winding coupled between a voltage source and the gate of the first transistor, and

the second transformer comprises a third winding coupled between the power supply source and the drain terminal of the second transistor, and a fourth winding coupled between the voltage source and the gate of the second transistor.

3. The VCO of claim 2, further comprising:

a first coupling device coupled between the drain terminal of the first transistor and one of the gate of the first transistor or the gate of the second transistor; and

a second coupling device coupled between the drain terminal of the second transistor and the other of the gate of the first transistor or the gate of the second transistor.

4. The VCO of claim 3, wherein each of the first coupling device and the second coupling device comprises a capacitive device.

5. The VCO of claim 4, wherein each of the first coupling device and the second coupling device further comprises an inductive device in series with or in parallel with the capacitive device.

6. The VCO of claim 2, further comprising a bypass capacitor coupled to the power supply source and parallel to each of the first winding in series with the first transistor and the third winding in series with the second transistor.

7. An oscillator comprising:

a first node configured to have a first bias voltage;

a second node configured to have a second bias voltage;

a reference node configured to have a reference voltage;

an output terminal;

a forward stage comprising a first terminal coupled to the output terminal and a second terminal coupled to one of the first node, the second node, or the reference node; and

a transformer-coupled band-pass filter (BPF) coupled between the output terminal and a third terminal of the forward stage.

8. The oscillator of claim 7, wherein the transformer-coupled BPF comprises a capacitive device coupled between the output terminal and the third terminal of the forward stage.

9. The oscillator of claim 8, wherein the transformer-coupled BPF further comprises an inductive device coupled in series or in parallel with the capacitive device between the output terminal and the third terminal of the forward stage.

10. The oscillator of claim 7, wherein the transformer-coupled BPF comprises a first winding coupled between the third terminal of the forward stage and the reference node, and a second winding coupled between the output terminal and the reference node.

11. The oscillator of claim 7, wherein the second bias voltage has a value relative to a value of the reference voltage greater than a value of the first bias voltage relative to the value of the reference voltage.

12. The oscillator of claim 7, wherein

the forward stage comprises a transistor, the transistor comprising a drain terminal corresponding to the first terminal, a source terminal corresponding to the second terminal coupled to the reference node, and a gate corresponding to the third terminal, and

the transformer-coupled BPF comprises a first center tap coupled to the first node and a second center tap coupled to the second node.

13. The oscillator of claim 7, wherein

the forward stage comprises a transistor, the transistor comprising a source terminal corresponding to the first terminal, a gate corresponding to the second terminal coupled to the first node, and a drain terminal corresponding to the third terminal, and

the transformer-coupled BPF comprises a center tap coupled to the second node.

14. The oscillator of claim 7, wherein

the forward stage comprises a transistor, the transistor comprising a drain terminal corresponding to the first terminal, a gate corresponding to the second terminal coupled to the first node, and a source terminal corresponding to the third terminal, and

the transformer-coupled BPF comprises a center tap coupled to the second node.

15. The oscillator of claim 7, wherein

the forward stage comprises a transistor, the transistor comprising a source terminal corresponding to the first terminal, a drain terminal corresponding to the second terminal coupled to the second node, and a gate corresponding to the third terminal, and

the transformer-coupled BPF comprises a center tap coupled to the first node.

16. A differential oscillator comprising:

a differential circuit coupled between a first output node and a second output node; and

a transformer-coupled band-pass filter (BPF) coupled between the first output node and the second output node, the transformer-coupled BPF comprising;

a coupling device coupled between the first output node and the second output node; and

a transformer comprising;

a first winding coupled between the first output node and a voltage node; and

a second winding coupled between the second output node and the voltage node.

17. The differential oscillator of claim 16, wherein the voltage node is configured to have a ground voltage.

18. The differential oscillator of claim 16, wherein the differential circuit comprises a cross-coupled pair of transistors.

19. The differential oscillator of claim 16, wherein the coupling device comprises a capacitive device coupled between the first output node and the second output node.

20. The oscillator of claim 19, wherein the coupling device further comprises an inductive device coupled in series or in parallel with the capacitive device between the first output node and the second output node.