A system for testing a subject transistor with constant power. The system may include an amplifier, a measurement voltage source, and a exercise voltage source. The amplifier may have an output connected to a gate of the subject transistor. The amplifier may have a first input and a second input. The measurement voltage source may be connected to the first input of the amplifier for use in measuring characteristics of the subject transistor. The exercise voltage source may be connected to the first input of the amplifier for exercising the subject transistor. The second input of the amplifier may be connected to a source of the subject transistor through a resistor.

An envelope tracking (ET) radio frequency (RF) front-end circuit is provided. The ET RF front-end circuit includes an ET integrated circuit(s) (ETIC(s)), a local transceiver circuit, a target voltage circuit(s), and a number of power amplifiers. The local transceiver circuit receives an input signal(s) from a coupled baseband transceiver and generates a number of RF signals. The target voltage circuit(s) generates a time-variant ET target voltage(s) based on the input signal(s). The ETIC(s) generates multiple ET voltages based on the time-variant ET target voltage(s). The power amplifiers amplify the RF signals based on the ET voltages. Given that the time-variant ET target voltage(s) is generated inside the self-contained ET RF front-end circuit, it is possible to reduce distortion in the time-variant ET target voltage(s), thus helping to improve operating efficiency of the power amplifiers, especially when the RF signals are modulated with a higher modulation bandwidth (e.g., ≥200 MHz).

A transformer-based amplifier, an operating method thereof, and devices including the same are disclosed. A millimeter wave amplifier includes a first transformer positioned on an input side of the millimeter wave amplifier, a second transformer positioned on an output side of the millimeter wave amplifier, and one or more of amplification stages positioned between the first transformer and the second transformer.

A radio-frequency module includes a multilayer substrate, a first semiconductor device, a second semiconductor device, a mold layer, and a shield layer. The multilayer substrate includes a plurality of stacked layers, and has a first major face and a second major face. The mold layer seals at least the second semiconductor device. The shield layer 80 covers the mold layer. The first major face includes a first recess. The first semiconductor device is mounted over a bottom face of the first recess. The second semiconductor device is mounted over the first major face so as to overlie the first recess. The first semiconductor device is connected with a metallic via that extends through a portion of the multilayer substrate from the bottom face of the first recess to the second major face. The mold layer does not cover a top face of the second semiconductor device.

A transceiver is configured for a calibration mode of operation in which an impedance of a transmit chain is tuned responsive to a power measurement of a mixed RF calibration signal to form a tuned transmit chain. A direct conversion mixes an RF calibration signal with a DC offset signal to form the mixed calibration signal. During a normal mode of operation, a heterodyne mixer mixes an LO signal with an IF signal to produce an RF signal that is amplified through the tuned transmit chain.

A transimpedance amplifier circuit (1) includes an amplifier (22) that amplifies a received signal, an automatic gain control (AGC) circuit (2) that controls the amplification gain of the amplifier by a first time constant in accordance with the level of the received signal, and a first selection circuit (25) that selects the first time constant from a plurality of predetermined values. This can simultaneously implement a short time constant of an AGC function necessary to instantaneously respond to a burst signal and a long time constant of the AGC function necessary to obtain a satisfactory bit error rate (BER) characteristic in a continuous signal by an inexpensive and compact circuit arrangement.

An instrumentation amplifier that includes input capacitance cancellation is provided. The architecture includes programmable capacitors between the input stage and a current feedback loop of the instrumentation amplifier to cancel input capacitances from electrode cables and a printed circuit board at the front end. An on-chip calibration unit can be employed to calibrate the programmable capacitors and improve the input impedance.

Power amplifiers for amplifying a radio frequency signal are provided. The power amplifier may include an envelope tracking power supply, a carrier amplifier coupled with the envelope tracking power supply and configured to amplify the radio frequency signal, an input matching network configured to split the amplified radio frequency signal from the carrier amplifier such that one part of the amplified radio frequency signal passes along a peak amplifier path and another part of the amplified radio frequency signal passes along an impedance transformer path, a peak amplifier coupled with the envelope tracking power supply and configured to amplify the one part of the amplified radio frequency signal from the input matching network, an impedance transformer configured to perform impedance transformation on the other part of the amplified radio frequency signal from the input matching network, an output matching network configured to combine the output of the peak amplifier and the impedance transformer, wherein the peak amplifier is configured to be switched off in a lower power mode and switched on in a high power mode based at least in part on an input power level of the radio frequency signal. With the claimed solutions, more powerful and efficient power amplifiers that are capable of operating over broader frequency ranges may be achieved.

A method may be provided for powering up or down a playback path comprising a digital-to-analog converter (DAC) for generating a non-ground-centered analog intermediate voltage centered at a common-mode voltage and coupled to a driver for generating a ground-centered playback path output voltage at an output of the driver wherein the output of the driver is clamped via a finite impedance to a ground voltage. The method may include transitioning continuously or in a plurality of discrete steps the analog intermediate voltage from an initial voltage to the common-mode voltage such that the transitioning is substantially inaudible at the output of the driver. A method for operating an output clamp of an output driver stage of a playback path may include transitioning continuously or in a plurality of discrete steps an impedance of the output clamp in order to match an output offset of the output driver stage in order to minimize audio artifacts appearing at an output of the output driver stage.

A power amplifier circuit includes first and second transistors and a first voltage output circuit. A radio frequency signal is input into a base of the first transistor. The first voltage output circuit outputs a first voltage in accordance with a power supply voltage. The first voltage is supplied to a base or a gate of the second transistor. An emitter or a source of the second transistor is connected to a collector of the first transistor. A first amplified signal generated by amplifying the radio frequency signal is output from a collector or a drain of the second transistor.