According to one embodiment, a transformer-based in-phase and quadrature (IQ) includes a differential balun having a first inductor and a second inductor. The first inductor has a first input terminal and a first output terminal. The second inductor has a second input terminal and a second output terminal. Additionally, the IQ generator circuit includes a third inductor magnetically coupled with the first inductor. The third inductor has a first isolation terminal and a third output terminal. The IQ generator circuit also includes a fourth inductor magnetically coupled with the second inductor. The fourth inductor has a second isolation terminal and a fourth output terminal. The IQ generator circuit additionally includes a first transistor coupled to the first input terminal of the first inductor. Further, the generator circuit includes a second transistor coupled to the second input terminal of the second inductor. The first transistor, the second transistor, the first inductor, and the second inductor form a part of a differential amplifier.

A high-power, high-frequency radio frequency power amplifier includes an output stage and a single-phase driver. The output stage is arranged in a Class-D amplifier configuration and includes a first depletion mode field effect transistor (FET), a second depletion mode FET, and a bootstrap path that couples the output of the output stage to the gate of the second FET. The first and second depletion mode FETs are switched out-of-phase and between fully-ON and fully-OFF states, under the direction of the single-phase driver. The single-phase driver directly controls the ON/OFF state of the first depletion mode FET and provides a discharge path through which the input gate capacitor of the second depletion mode FET in the output stage can discharge to turn OFF the second depletion mode FET. The bootstrap path provides a current path through which the input gate capacitor of the second depletion mode FET can charge to turn the second depletion mode FET ON.

A wideband power amplifier (PA) linearization technique is proposed. A current interpolation technique is proposed to linearize power amplifiers over a wide bandwidth. The wideband power amplifier linearization technique employs a novel transconductance Gm linearizer using a current interpolation technique that achieves improvement in the third order intermodulation over wide bandwidth for a sub-micron CMOS differential power amplifier. By using a small amount of compensating bias into an opposite phase differential pair, linearization over wide bandwidth is achieved and can be optimized by adjusting the compensating bias.

A Doherty amplifier (10) according to the present invention includes: a distribution unit (11) that distributes input signals; a main amplifier (12) that amplifies a first distributed signal output from the distribution unit (11); a transmission line unit (13) that transmits the first distributed signal amplified by the main amplifier (12); a peak amplifier (14) that amplifies a second distributed signal output from the distribution unit (11); a transmission line unit (15) that transmits the second distributed signal amplified by the peak amplifier (14); a synthesizing unit (16) that synthesizes the first distributed signal and the second distributed signal, and outputs a synthesized signal; and an impedance transformation unit (17) that performs an impedance transformation of the synthesized signal output from the synthesizing unit (16). The impedance transformation unit (17) includes a plurality of λ/4 transmission lines connected in series.

Radio frequency (RF) amplification devices are disclosed that include Doherty amplification circuits and methods of operating the same. In one embodiment, a Doherty amplification circuit includes a main carrier RF amplifier, a peaking RF amplifier, and a periodic quadrature coupler. To provide Doherty amplification, the peaking RF amplifier is configured to be deactivated while an RF signal is below a threshold level and is configured to be activated while the RF signal is above the threshold level. The periodic quadrature coupler is configured to combine a first RF split signal from the main carrier RF amplifier and a second RF split signal from the peaking RF amplifier into the RF signal, such that the RF signal is output from an output port while the peaking RF amplifier is activated. The periodic quadrature coupler allows the Doherty amplification circuit to provide broadband amplification in various RF communication bands.

A wideband self-envelope tracking power amplifier (PA) can use more than a 40-MHz channel bandwidth and improves the envelope bandwidth limit of a self-envelope tracking PAs by ten times. The PA uses an envelope load network, which is based on a general multi-stage low-pass filter. The envelope load network located between an RF choke inductor and main DC power supply provides a dynamically modulated PA supply voltage without using a dedicated envelope amplifier. An input terminal of the network connects a main PA via an RF choke inductor to an input of low-pass filter. An output terminal is connected to the low-pass filter via an envelope choke inductor and to a direct current (DC) power supply. A DC blocker is connected between the output of the low-pass filter and ground by a termination resistor.

A wideband RF choke circuit includes an input, first and second nodes, and a splitting means coupled between the input, first node, and second node. A first all-pass filter and a first line AC blocker are coupled between the input and the splitting means. Second and third all-pass filters, and second and third line AC blockers, are coupled between the splitting means and the first and second nodes, respectively. A first RF choke has a first end, coupled to the first all-pass filter, and a second end. A second RF choke has a first end, coupled to the second end of the first RF choke, and a second end coupled to the second all-pass filter. A third RF choke has a first end, coupled to the second end of the first RF choke, and a second end coupled to the third all-pass filter.

Apparatus and methods for an inverted Doherty amplifier operating at gigahertz frequencies are described. RF fractional bandwidth and signal bandwidth may be increased over a conventional Doherty amplifier configuration when impedance-matching components and an impedance inverter in an output network of the inverted Doherty amplifier are designed based on characteristics of the main and peaking amplifier and asymmetry factor of the amplifier.

A die is described comprising at least one 3-way Doherty amplifier comprising a main stage, a first peak stage and a second peak stage. An input is connected to an input network which is connected to the main stage, first peak stage and second peak stage. The input network includes a first impedance connected to an input of the first peak stage and providing a −90° phase shift and a second impedance connected to an input of the second peak stage and providing a 90° phase shift. An output is connected to an output network which is connected to the main stage, first peak stage and second peak stage. The output network includes a third impedance connected to the output of the first peak stage and providing a 180° phase shift and a fourth impedance connected to the output of the main stage and providing a 90° phase shift.

Methods and apparatus for providing adaptive biasing to power amplifiers. Adaptive bias circuits are configured to provide sharp turn on and/or current clamping to improve the efficiency of a power amplifier over a wide input signal bandwidth. Sharp turn on may be achieved using a subtraction technique to subtract outputs from multiple detectors. Clamping may be achieved using MOSFET device characteristics to pull the device from the triode region into the saturation, subtraction techniques to subtract the outputs from multiple detectors, and/or by using circuit devices, such as diodes.