A high frequency power amplifier includes a first high frequency amplifier, a final high frequency amplifier, and a tunable filter. The tunable filter is connected between the first high frequency amplifier and the final high frequency amplifier. The first high frequency amplifier and the final high frequency amplifier are each a multimode/multiband power amplifier. The tunable filter is regulated such that its pass band includes the frequency band of a transmission signal and its attenuation band includes the frequency band of a reception signal in a communication band used in transmission and reception. The pass band and the attenuation band are switched by the tunable filter in accordance with the communication band used in transmission and reception.

An amplifier circuit having an improved inter-stage matching network and improved performance. In one embodiment, an RF signal source having an output impedance Z.sub.SOURCE is approximately impedance matched through an inductive tuning circuit to a power amplifier having an input impedance Z.sub.PA. The inductive tuning circuit includes a tunable capacitor element C1 and inductive elements L1, L2, which may be fabricated as stacked conductor coils. Since the capacitance of C1 is tunable, impedance matching is available over a broad range of RF frequencies. Also provided are DC isolation between the RF signal source and the power amplifier, coupling of a voltage source to the output of the RF signal source through L1, and coupling of a bias voltage to the input of the power amplifier through L2.

A current reuse FET amplifier according to the present invention provides an effect of reducing a variation of bias current of the amplifier, with gate voltage or a resistor for self-biasing of an FET of the amplifier changing in accordance with a process variation of saturation current Idss of the FET.

A power amplification circuit that includes: a capacitor element in which a first metal layer, a first insulating layer, a second metal layer, a second insulating layer and a third metal layer are sequentially stacked, the capacitor element including a first capacitor in which the first metal layer serves as one electrode thereof and the second metal layer serves as another electrode thereof, and a second capacitor in which the second metal layer serves as one electrode thereof and the third metal layer serves as another electrode thereof; and a transistor that amplifies a radio-frequency signal. The radio-frequency signal is supplied to the one electrode of the first capacitor. The other electrode of the first capacitor and the one electrode of the second capacitor are connected to a base of the transistor, and the other electrode of the second capacitor is connected to the emitter of the transistor.

A two-stage amplifier of a type of the current re-use configuration is disclosed. The amplifier includes first to third transistors, where the first transistor constitute the first stage, while, the latter two transistors constitute the second stance. The first to third transistors are connected in series between a power supply and ground such that a bias current supplied to the third transistor flows in the second and first transistors. The first transistor in the source thereof is grounded in the DC mode. The second transistor is grounded in the AC mode but floated in the DC mode. The third transistor that outputs an amplified signal is connected in parallel in the AC mode but in series in the DC mode with respect to the second transistor.

Aspects of this disclosure relate to an amplification circuit that includes a stacked amplifier and a bias circuit. The stacked amplifier includes at least a first transistor and a second transistor in series with each other. The stacked amplifier is operable in at least a first mode and a second mode. The bias circuit is configured to bias the second transistor to a linear region of operation in the first mode and to bias the second transistor as a switch in the second mode. In certain embodiments, the amplification circuit can be a power amplifier stage configured to receive a supply voltage that has a different voltage level in the first mode than in the second mode.

Embodiments of the present disclosure describe apparatuses, methods, and systems of front end module (FEM) having a feedback path that includes a passive attenuation network. The passive attenuation network may provide a feedback signal to a receive output port of the FEM that may be used as a basis for predistortion. Other embodiments may also be described and/or claimed.

A high-frequency signal amplifier circuit is used in a front-end circuit configured to propagate a high-frequency transmission signal and a high-frequency reception signal, and includes an amplifier transistor configured to amplify the high-frequency transmission signal; a bias circuit configured to supply a bias to a signal input end of the amplifier transistor; and a ferrite bead, one end of which is connected to a bias output end of the bias circuit and the other end of which is connected to the signal input end of the amplifier transistor, having characteristics in which impedance in a difference frequency band between the high-frequency transmission signal and the high-frequency reception signal is higher than impedance in DC.

Disclosed is a transimpedance amplifier, comprising a first-stage trans-conductance amplifier TCA, a second-stage TCA, a third-stage amplifier and a feedback circuit. The first-stage TCA is electrically connected to an input current source to receive a first input signal, and outputs a first output signal. The second-stage TCA is electrically connected to the first-stage TCA to receive the first output signal, and outputs a second output signal. The third-stage amplifier is electrically connected to the second-stage TCA to receive the second output signal, and outputs a third output signal. One end of the feedback circuit is electrically connected to the input of the first-stage TCA, and the other end of the feedback circuit is electrically connected to the output of the third-stage amplifier to stabilize the third output signal. The third-stage amplifier is composed of a first output stage and a second output stage.

A high-performance HBT that is unlikely to decrease the process controllability and to increase the manufacturing cost is implemented. A heterojunction bipolar transistor includes an emitter layer, a base layer, and a collector layer on a GaAs substrate. The emitter layer is formed of InGaP. The base layer is formed of GaAsPBi having a composition that substantially lattice-matches GaAs.