Amplification circuit

Abstract

An amplifier circuit includes a signal input terminal, a signal output terminal, a first transistor, a second transistor, a capacitor, and a shunt circuit. The signal input terminal is used to receive radio frequency (RF) signals. The signal output terminal is used to output amplified RF signals. The first transistor includes a first terminal coupled to the signal input terminal, a second terminal coupled to the signal output terminal, and a third terminal. The second transistor includes a first terminal, a second terminal, and a third terminal coupled to the first terminal of the first transistor. The capacitor is coupled between the third terminal of the second transistor and a reference voltage terminal. The shunt circuit includes a first terminal coupled to the third terminal of the second transistor, and a second and third terminal coupled to the first terminal of the capacitor. The shunt circuit provides a shunt current based on the voltage at the first terminal of the capacitor.

Claims

1. An amplifier circuit, comprising: A signal input terminal for receiving a radio frequency signal; One signal output terminal, used to output an amplified radio frequency signal; A first transistor includes: a first terminal coupled to the signal input terminal, a second terminal coupled to the signal output terminal, and a third terminal coupled to a first reference voltage terminal; a second transistor includes: a first terminal, a second terminal coupled to a voltage terminal, and a third terminal coupled to the first terminal of the first transistor; a first capacitor includes: a first terminal coupled to the third terminal of the second transistor, and a second terminal coupled to a second reference voltage terminal; and a shunt circuit includes: a first terminal coupled to the first terminal of the first capacitor, a second terminal coupled to the third terminal of the second transistor, and a third terminal coupled to a third reference voltage terminal, wherein the shunt circuit provides a shunt current based on a voltage at the first terminal of the first capacitor.

2. The amplifier circuit as described in claim 1, further comprising: A first inductor includes: a first terminal coupled to the third terminal of the second transistor, and a second terminal coupled to the first terminal of the first capacitor.

3. The amplifier circuit as described in claim 1, wherein, The shunt circuit further includes: a third transistor, comprising: a first terminal coupled to the first terminal of the first capacitor, a second terminal coupled to the third terminal of the second transistor, and a third terminal coupled to the third reference voltage terminal, wherein the third transistor is turned on or off according to the voltage at the first terminal of the first capacitor.

4. The amplifier circuit as described in claim 3, wherein, The shunt circuit further includes: a first resistor, comprising: a first terminal coupled to the first terminal of the first capacitor, and a second terminal coupled to the first terminal of the third transistor.

5. The amplifier circuit as described in claim 3, wherein: When the voltage at the first terminal of the first capacitor is lower than a first threshold, the third transistor is turned off. When the voltage at the first terminal of the first capacitor is equal to or exceeds the first threshold, the third transistor is turned on to provide the shunt current, wherein the shunt current flows from the second terminal of the third transistor to the third terminal of the third transistor.

6. The amplifier circuit as described in claim 3, further comprising: A substrate, wherein a first inductor and a first capacitor are disposed on the substrate, wherein the substrate includes: a first pad coupled to a first end of the first inductor and coupled to a third end of the second transistor; and a second pad coupled to a second end of the first inductor, the first end of the first capacitor, and coupled to a first resistor.

7. The amplifier circuit as described in claim 3, wherein, The first transistor and the third transistor are the same type of transistor and have the same turn-on threshold voltage.

8. The amplifier circuit as claimed in claim 1, further comprising: A source circuit, coupled to the first terminal of the second transistor, is used to provide a reference current.

9. The amplifier circuit as described in claim 8, wherein, The second transistor provides a buffer current based on the reference current, the buffer current flowing from the second terminal of the second transistor to the third terminal of the second transistor.

10. The amplifier circuit as claimed in claim 9, wherein: When the voltage at the first terminal of the first capacitor is lower than a first threshold, the shunt circuit is turned off; when the voltage at the first terminal of the first capacitor is equal to or exceeds the first threshold, the shunt circuit is turned on to provide the shunt current.

11. The amplifier circuit as claimed in claim 10, wherein: When the shunt circuit is turned on, a voltage at the third terminal of the second transistor reaches a predetermined value, and the predetermined value corresponds to a turn-on threshold voltage of the first transistor.

12. The amplifier circuit as described in claim 8, wherein, The source circuit includes: a fourth transistor, comprising: a first terminal, a second terminal coupled to the first terminal of the fourth transistor, and a third terminal coupled to a fourth reference voltage terminal; a fifth transistor, comprising: a first terminal coupled to the first terminal of the second transistor, a second terminal coupled to the first terminal of the fifth transistor, and a third terminal coupled to the second terminal of the fourth transistor; and a current source coupled to the second terminal of the fifth transistor for providing the reference current.

13. The amplifier circuit as described in claim 8, wherein, The source circuit includes: a first diode, including: a first terminal coupled to a fourth reference voltage terminal, and a second terminal; a second diode, including: a first terminal coupled to the second terminal of the first diode, and a second terminal coupled to the first terminal of the second transistor; and a current source coupled to the second terminal of the second diode for providing the reference current.

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