Power amplifier system with a clamp circuit for protecting the power amplifier system
According to at least one example of the disclosure, a power amplifier system is provided comprising an amplifying transistor configured to amplify a radio frequency signal, a bias circuit configured to provide a bias voltage to the amplifying transistor, and a clamp circuit for protecting the power amplifier system by absorbing a current flowing through the amplifying transistor when the clamp circuit is switched on. The clamp circuit is connected at a bias node between the bias circuit and the amplifying transistor and includes a clamp transistor and a clamp diode, the clamp diode having one end connected to a collector of the clamp transistor at the bias node and another end connected to a base of the clamp transistor.
1 . A power amplifier system comprising:
an amplifying transistor configured to amplify a radio frequency signal;
a bias circuit configured to provide a bias voltage to the amplifying transistor; and
a clamp circuit for protecting the power amplifier system by absorbing a current flowing through the amplifying transistor when the clamp circuit is switched on, the clamp circuit being connected at a bias node between the bias circuit and the amplifying transistor and including a clamp transistor and a clamp diode, the clamp diode having one end connected to a collector of the clamp transistor at the bias node and another end connected to a base of the clamp transistor.
2 . The power amplifier system of claim 1 wherein the clamp circuit is configured to prevent a current from flowing into the clamp circuit when the clamp circuit is switched off.
3 . The power amplifier system of claim 1 wherein the clamp circuit is configured to be switched on when a bias voltage exceeds a threshold voltage.
4 . The power amplifier system of claim 1 wherein the collector of the clamp transistor is connected between the bias node at which the bias voltage is provided and a ground.
5 . The power amplifier system of claim 1 wherein the bias node is connected to a base of the amplifying transistor via a resistor.
6 . The power amplifier system of claim 1 further comprising a voltage supply circuit configured to provide a supply voltage to the power amplifier system, the supply voltage having stepwise values that change periodically in relation to an output power of the power amplifier system.
7 . The power amplifier system of claim 1 further comprising a diode stack circuit including a plurality of diodes, the diode stack circuit connected between a collector of the amplifying transistor and an emitter of the amplifying transistor.
8 . The power amplifier system of claim 7 wherein the diode stack circuit includes a plurality of diodes connected in series, a single diode connected in parallel and in opposite direction to the plurality of diodes, and a capacitor connected in parallel to the plurality of diodes.
9 . A radio frequency module comprising:
a packaging substrate configured to receive a plurality of components; and
a power amplifier system implemented on the packaging substrate, the power amplifier system including an amplifying transistor configured to amplify a radio frequency signal, a bias circuit configured to provide a bias voltage to the amplifying transistor, and a clamp circuit for absorbing a current flowing through the amplifying transistor when the clamp circuit is switched on, the clamp circuit being connected at a bias node between the bias circuit and the amplifying transistor and including a clamp transistor and a clamp diode, the clamp diode having one end connected to a collector of the clamp transistor at the bias node and another end connected to a base of the clamp transistor.
10 . The radio frequency module of claim 9 wherein the radio frequency module is a front-end module.
11 . The radio frequency module of claim 9 wherein the clamp circuit is configured to prevent a current from flowing into the clamp circuit when the clamp circuit is switched off.
12 . The radio frequency module of claim 11 wherein the clamp circuit is configured to be switched on when a bias voltage exceeds a threshold voltage.
13 . The radio frequency module of claim 12 wherein the power amplifier system further includes a diode stack circuit including a plurality of diodes, the diode stack circuit connected between a collector of the amplifying transistor and an emitter of the amplifying transistor.
14 . The radio frequency module of claim 13 wherein the diode stack circuit includes a plurality of diodes connected in series, a single diode connected in parallel and in opposite direction to the plurality of diodes, and a capacitor connected in parallel to the plurality of diodes.
15 . The radio frequency module of claim 9 wherein the collector of the clamp transistor is connected between the bias node at which the bias voltage is provided and a ground.
16 . The radio frequency module of claim 9 wherein the bias node is connected to a base of the amplifying transistor via a resistor.
17 . The radio frequency module of claim 9 wherein the power amplifier system further includes a voltage supply circuit configured to provide a supply voltage to the power amplifier system, the supply voltage having stepwise values that change periodically in relation to an output power of the power amplifier system.
18 . The radio frequency module of claim 9 wherein the power amplifier system further includes a diode stack circuit including a plurality of diodes, the diode stack circuit connected between a collector of the amplifying transistor and an emitter of the amplifying transistor.
19 . The radio frequency module of claim 18 wherein the diode stack circuit includes a plurality of diodes connected in series, a single diode connected in parallel and in opposite direction to the plurality of diodes, and a capacitor connected in parallel to the plurality of diodes.
20 . The radio frequency module of claim 9 wherein the clamp circuit is configured to be switched on when a bias voltage exceeds a threshold voltage.