Inductor equivalent circuit and application thereof

• US 20040008096A1
• Filed: 01/15/2003
• Published: 01/15/2004
• Est. Priority Date: 02/01/2002
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Fan, Cheng-Hsuan, Hwang, Kent, Liu, Jing-Meng, Chuang, Chao-Hsuan
• Granted Patent: US 6,809,616 B2
• Time in Patent Office: Days
• US Class Current: 333/214
• CPC Class Codes: H03H 11/48 simulating reactances
• CPC Class Codes: H03H 11/485 Simulating inductances using operational amplifiers

Abstract

An inductor equivalent circuit is disclosed. The circuit comprises a reference current source, a first current mirror, a second current mirror, two operational amplifiers OP1 and OP2, a capacitor, a first transistor, a second transistor, a mirror resistor set, and a bypass current source in parallel with the capacitor. An input signal is through OP1 and second transistor to control the reference current source. The first mirror current is then feed-back a signal to the first transistor through an OP2. The current signal makes the drain current of the first transistor lags the input voltage signal by 90° due to the capacitor coupled with the first mirror current source. The mirror resistor set can be resistors having one common terminal grounded, and other terminals each, respectively, coupled with the first and the second transistor and the capacitor, or can be composed of transistors and all of them with gate property biased so that the transistors in the mirror resistor set are operated in an ohmic region. The second mirror current provides an output current of the inductor equivalent circuit for next cascade stage.

Claims

1. An inductor equivalent circuit comprising:

a first resistor R₁ having one terminal connected to ground;

a second resistor R₂ having one terminal connected to ground;

a capacitor C₁ having one terminal connected to ground;

a first transistor having a drain terminal coupling with an input signal and a source terminal coupling with said first resistor R₁;

a second transistor having a source terminal coupling with said second resistor R₁ and a gate terminal coupling said input signal;

a current mirror having a third transistor and a fourth transistor and having gate terminals thereof connecting to a source terminal of said third transistor to provide a reference current and a mirror current through said fourth transistor, and said fourth transistor having a source terminal coupling with said capacitor,

a direct current source in parallel with said capacitor; and

thus constructing an equivalent inductor with a value about C₁R₂R₁/n, wherein said n is a ratio of (W/L)₄/(W/L)₃, where (W/L)₄ is the channel width over the channel length of said fourth transistor and (W/L)₃ is the channel width over the channel length of said third transistor.

2. The inductor equivalent circuit of claim 1, further comprises a first operational amplifier having an output terminal coupled with said gate terminal of said second transistor, and having a first input terminal coupled with said input signal and a second input terminal coupled with said source terminal of said second transistor.

3. The inductor equivalent circuit of claim 1, wherein said third transistor and fourth transistor belong to a p type MOS transistor and said first transistor and second transistor belong to an n type MOS transistor.

4. The inductor equivalent circuit of claim 1, further comprises a second operational amplifier having an output terminal coupled with said gate terminal of said first transistor, and having a first input terminal coupled with said source terminal of said fourth transistor, and a second input terminal coupled with said source terminal of said first transistor.

5. The inductor equivalent circuit of claim 1, further comprises a fifth transistor having a gate coupled with said gate terminal of said fourth transistor so that the source terminal can provide a current output of said inductor equivalent circuit.

6. The inductor equivalent circuit of claim 1, further comprises a damped resistor connect in between said capacitor and ground to stabilize said inductor equivalent circuit.

7. An inductor equivalent circuit comprising:

a first transistor having a source terminal grounded;

a second transistor having a source terminal grounded, wherein said first transistor and said second transistor having gates thereof connecting to a gate bias signal, which enables said first transistor and said second transistor operate at ohmic region;

a third transistor having a drain terminal coupling with an input signal and a source terminal coupling with said first transistor;

a fourth transistor having a source terminal coupling with said second transistor and a gate terminal coupling said input signal;

a capacitor having one terminal connected to ground;

a current mirror having a fifth transistor, a sixth transistor, and seventh transistor and having gate terminals thereof connecting to a source terminal of said fifth transistor to provide a reference current through said fifth transistor and a first mirror current through said sixth transistor, and a second mirror current through said seventh transistor furthermore said sixth transistor having a source terminal coupling with said capacitor,

a direct current source in parallel with said capacitor; and

thus constructing an equivalent inductor with a value about C₁R₂R₁/n, where R₁, R₂ are equivalent resistances of said first transistor and said second transistor., and wherein said n is a ratio of (W/L)₄/(W/L)₃, where (W/L)₄ is the channel width over the channel length of said fourth transistor and (W/L)₃ is the channel width over the channel length of said third transistor.

8. The inductor equivalent circuit of claim 7, further comprises a first operational amplifier having an output terminal coupled with said gate terminal of said fourth transistor, and having a first input terminal coupled with said input signal and a second input terminal coupled with said source terminal of said fourth transistor.

9. The inductor equivalent circuit of claim 7, further comprises a second operational amplifier having an output terminal coupled with said gate terminal of said third transistor, and having a first input terminal coupled with said source terminal of said third transistor, and a second input terminal coupled with said source terminal of said third transistor.

10. The inductor equivalent circuit of claim 7, further comprises an eighth transistor having a gate terminal coupled with said gate terminal of said second transistor, and said eighth transistor is in between said capacitor and ground to stabilize said inductor equivalent circuit.

11. The inductor equivalent circuit of claim 7 or 10, wherein said fifth, said sixth and said seventh transistor belong to a p type MOS transistor and said first, said second, said third, said fourth transistor and said eighth transistor belong to a n type MOS transistor.

12. The inductor equivalent circuit of claim 7 wherein said fifth, said sixth and said seventh transistor can have different channel width over the channel length ratio so that said reference current, said first mirror current and said second mirror current are dependent each other.

13. The inductor equivalent circuit of claim 7 wherein said first, said second and said eighth transistor can have the same or different channel width over the channel length ratio, and each of them acts as a resistor and said gate bias signal make them operate in ohmic region.