A semiconductor device includes a semiconductor substrate including a principal surface parallel to a plane defined by a first direction and a second direction substantially orthogonal to the first direction, and the principal surface having a first side parallel to the first direction; first unit transistors, each amplifying a first signal in a first frequency band to output a second signal; and second unit transistors, each amplifying the second signal to output a third signal and aligned in the second direction between the first side and a substrate center line in the first direction in plan view of the principal surface. A first center line in the first direction of a region in which the first unit transistors are aligned is farther from the first side than a second center line in the first direction of a region in which the second unit transistors are aligned.

A semiconductor device includes a semiconductor substrate including a principal surface parallel to a plane defined by a first direction and a second direction substantially orthogonal to the first direction, and the principal surface having a first side parallel to the first direction; first unit transistors, each amplifying a first signal in a first frequency band to output a second signal; and second unit transistors, each amplifying the second signal to output a third signal and aligned in the second direction between the first side and a substrate center line in the first direction in plan view of the principal surface. A first center line in the first direction of a region in which the first unit transistors are aligned is farther from the first side than a second center line in the first direction of a region in which the second unit transistors are aligned.

A variable-gain power amplifying technique includes generating, with a network of one or more reactive components included in an oscillator, a first oscillating signal, and outputting, via one or more taps included in the network of the reactive components, a second oscillating signal. The second oscillating signal has a magnitude that is proportional to and less than the first oscillating signal. The power amplifying technique further includes selecting one of the first and second oscillating signals to use for generating a power-amplified output signal, and amplifying the selected one of the first and second oscillating signals to generate the power-amplified output signal.

A variable-gain power amplifying technique includes generating, with a network of one or more reactive components included in an oscillator, a first oscillating signal, and outputting, via one or more taps included in the network of the reactive components, a second oscillating signal. The second oscillating signal has a magnitude that is proportional to and less than the first oscillating signal. The power amplifying technique further includes selecting one of the first and second oscillating signals to use for generating a power-amplified output signal, and amplifying the selected one of the first and second oscillating signals to generate the power-amplified output signal.

Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can have a varying supply voltage. According to one aspect, the gate of the input transistor of the amplifier is biased with a fixed voltage whereas the gates of the other transistors of the amplifier are biased with variable voltages that are linear functions of the varying supply voltage. According to another aspect, the linear functions are such that the variable voltages coincide with the fixed voltage at a value of the varying supply voltage for which the input transistor is at the edge of triode. According to another aspect, biasing of the stacked transistors is such that, while the supply voltage varies, the drain-to-source voltage of the input transistor is maintained to a fixed value whereas the drain-to-source voltages of all other transistors are equal to one another.

Voltage stabilizing and voltage regulating circuits implemented in GaN HEMT technology provide stable output voltages suitable for use in applications such as GaN power transistor gate drivers and low voltage auxiliary power supplies for GaN integrated circuits. Gate driver and voltage regulator modules include at least one GaN D-mode HEMT (DHEMT) and at least two GaN E-mode HEMTs (EHEMTs) connected together in series, so that the at least one DHEMT operates as a variable resistor and the at least two EHEMTs operate as a Zener diode that limits the output voltage. The gate driver and voltage regulator modules may be implemented as a GaN integrated circuits, and may be monolithically integrated together with other components such as amplifiers and power HEMTs on a single die to provide a GaN HEMT power module IC.

Voltage stabilizing and voltage regulating circuits implemented in GaN HEMT technology provide stable output voltages suitable for use in applications such as GaN power transistor gate drivers and low voltage auxiliary power supplies for GaN integrated circuits. Gate driver and voltage regulator modules include at least one GaN D-mode HEMT (DHEMT) and at least two GaN E-mode HEMTs (EHEMTs) connected together in series, so that the at least one DHEMT operates as a variable resistor and the at least two EHEMTs operate as a Zener diode that limits the output voltage. The gate driver and voltage regulator modules may be implemented as a GaN integrated circuits, and may be monolithically integrated together with other components such as amplifiers and power HEMTs on a single die to provide a GaN HEMT power module IC.

Systems and methods according to one or more embodiments are provided for correcting a current measurement through a speaker in an audio system. In one example, a system for driving a speaker includes an output stage configured to drive a current through the speaker. The system further includes a first and second current sensor coupled to the output stage and configured to measure a positive current including a first measurement error and a negative current including a second measurement error through the speaker, respectively. The system further includes a processing block coupled to the first and second current sensors to receive the measured positive and negative current signals and configured to add a positive offset value to an input of each first and second current sensors, determine the first and second measurement errors, and correct a measured current using the positive and negative currents and the determined first and second measurement errors.

Systems and methods according to one or more embodiments are provided for correcting a current measurement through a speaker in an audio system. In one example, a system for driving a speaker includes an output stage configured to drive a current through the speaker. The system further includes a first and second current sensor coupled to the output stage and configured to measure a positive current including a first measurement error and a negative current including a second measurement error through the speaker, respectively. The system further includes a processing block coupled to the first and second current sensors to receive the measured positive and negative current signals and configured to add a positive offset value to an input of each first and second current sensors, determine the first and second measurement errors, and correct a measured current using the positive and negative currents and the determined first and second measurement errors.

This disclosure relates to methods of forming bipolar transistors, such as heterojunction bipolar transistors. The methods may include forming a sub-collector over a substrate, forming a first portion of a collector over the sub-collector and doping a second portion of the collector to form a doping spike. The method may further include forming a third portion of the collector over the doping spike and forming a base of the bipolar transistor over the third portion of the collector.