Power amplifier bias signal multiplexing
A power amplifier (PA) system includes an amplifying transistor having a base, a collector, and an emitter. The PA system further includes a radio-frequency (RF) input configured to receive an RF input signal having an RF component and a DC bias component, a bias circuit coupled to the base of the amplifying transistor, and a bias tee circuit configured to receive the RF input signal and pass at least a portion of the DC component to the bias circuit and at least a portion of the RF component to the base of the amplifying transistor.
1. A power amplifier system comprising:
an amplifying transistor having a base, a collector, and an emitter;
a radio-frequency input configured to receive a radio-frequency input signal having a radio-frequency component and a DC bias component;
a bias circuit coupled to the base of the amplifying transistor; and
a bias tee circuit configured to receive the radio-frequency input signal and pass at least a portion of the DC component to the bias circuit and at least a portion of the radio-frequency component to the base of the amplifying transistor.
2. The power amplifier system of claim 1 wherein the bias tee circuit operates to at least partially decouple the radio-frequency component from the DC bias component.
3. The power amplifier system of claim 1 wherein the bias tee includes an inductor and a resistor.
4. The power amplifier system of claim 1 further comprising a voltage supply input configured to receive a supply voltage for amplifying an output of the amplifying transistor.
5. The power amplifier system of claim 1 wherein the DC bias component of the radio-frequency input signal includes a bias current.
6. The power amplifier system of claim 1 wherein the DC bias component of the radio-frequency input signal includes a bias voltage.
7. The power amplifier system of claim 1 wherein the bias circuit includes current mirror circuitry.
8. A method for biasing a power amplifier, the method comprising:
providing a radio-frequency input signal to a power amplifier module, the radio-frequency input signal having a radio-frequency component and a DC bias component;
decoupling the DC bias component of the radio-frequency input signal from the radio-frequency component;
providing the decoupled DC bias component to a bias circuit coupled to a base of an amplifying transistor of the power amplifier module;
providing the decoupled radio-frequency component to the base of the amplifying transistor; and
generating a radio-frequency output signal using the amplifying transistor.
9. The method of claim 8 wherein said decoupling the DC bias component from the radio-frequency component is performed using a bias tee including an inductor and a resistor.
10. The method of claim 8 further comprising providing a supply voltage to the amplifying transistor.
11. The method of claim 8 wherein the DC bias component of the radio-frequency input signal includes a bias current.
12. The method of claim 8 wherein the DC bias component of the radio-frequency input signal includes a bias voltage.
13. The method of claim 8 wherein the bias circuit includes current mirror circuitry.
14. A radio-frequency module comprising:
a packaging substrate configured to receive a plurality of components;
a power amplifier die mounted on the packaging substrate, the power amplifier die including a first semiconductor substrate having formed thereon an amplifying transistor having a base, a collector, and an emitter;
a radio-frequency input to the power amplifier die configured to receive a radio-frequency input signal having a radio-frequency component and a DC bias component;
a bias circuit implemented on the first semiconductor substrate, the bias circuit coupled to the base of the amplifying transistor;
a first bias tee circuit implemented on the first semiconductor substrate, the first bias tee circuit configured to receive the radio-frequency input signal and at least partially pass the DC bias component to the bias circuit and the radio-frequency component to the base of the amplifying transistor; and
a plurality of connectors configured to provide electrical connections between the power amplifier die and the packaging substrate.
15. The radio-frequency module of claim 14 further comprising:
a controller die mounted on the packaging substrate, the controller die including a second semiconductor substrate and a bias signal generator configured to transmit a bias signal on a bias channel of the radio-frequency module; and
a radio-frequency transmission channel configured to transmit a radio-frequency signal within the radio-frequency module.
16. The RF module of claim 15 further comprising:
a second bias tee circuit coupled to the bias channel and the radio-frequency transmission channel, the second bias tee circuit configured to couple the bias signal with the radio-frequency signal to form the radio-frequency input signal at least in part.
17. The radio-frequency module of claim 15 wherein the bias signal generator is a current generator.
18. The radio-frequency module of claim 15 wherein the bias signal generator is a voltage generator.
19. The radio-frequency module of claim 15 wherein the controller die includes an input switching module implemented on the second semiconductor substrate.
20. The radio-frequency module of claim 15 wherein the first semiconductor substrate is a GaAs substrate and the second semiconductor substrate is a silicon-on-insulator die.