A coupler circuit includes: a signal line disposed between a first terminal and a second terminal; a coupling line disposed between a coupling port and an isolation port such that the coupling line is coupled to the signal line and is configured to extract a coupling signal from the signal line; and a coupling adjusting circuit connected to the coupling port and the isolation port, and configured to reduce changes in an amount of coupling according to a change in a frequency band of a signal passing through the signal line.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

One aspect of this disclosure is a power amplifier module that includes a power amplifier on a substrate and a semiconductor resistor on the substrate. The power amplifier includes a bipolar transistor having a collector, a base, and an emitter. The collector has a doping concentration of at least 310.sup.16 cm.sup.3 at an interface with the base. The collector also has at least a first grading in which doping concentration increases away from the base. The semiconductor resistor includes a resistive layer that that includes the same material as a layer of the bipolar transistor. Other embodiments of the module are provided along with related methods and components thereof.

One aspect of this disclosure is a power amplifier module that includes a power amplifier on a substrate and a semiconductor resistor on the substrate. The power amplifier includes a bipolar transistor having a collector, a base, and an emitter. The collector has a doping concentration of at least 310.sup.16 cm.sup.3 at an interface with the base. The collector also has at least a first grading in which doping concentration increases away from the base. The semiconductor resistor includes a resistive layer that that includes the same material as a layer of the bipolar transistor. Other embodiments of the module are provided along with related methods and components thereof.

A system for thermally protecting an amplifier driving a capacitive load may include a low-pass filter configured to filter, with a variable cutoff frequency, an input signal to generate a filtered input signal, wherein the amplifier is configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load and a controller configured to receive a real-time estimate of a temperature associated with the amplifier and vary the variable cutoff frequency as a function of the temperature.

A multiple-stage amplifier includes a driver stage die and a final stage die. The driver stage die includes a first type of semiconductor substrate (e.g., a silicon substrate), a first transistor, and an integrated portion of an interstage impedance matching circuit. A control terminal of the first transistor is electrically coupled to an RF signal input terminal of the driver stage die, and the integrated portion of the interstage impedance matching circuit is electrically coupled between a current-carrying terminal of the first transistor and an RF signal output terminal of the driver stage die. The second die includes a III-V semiconductor substrate (e.g., a GaN substrate) and a second transistor. A connection, which is a non-integrated portion of the interstage impedance matching circuit, is electrically coupled between the RF signal output terminal of the driver stage die and an RF signal input terminal of the final stage die.

A multiple-stage amplifier includes a driver stage die and a final stage die. The driver stage die includes a first type of semiconductor substrate (e.g., a silicon substrate), a first transistor, and an integrated portion of an interstage impedance matching circuit. A control terminal of the first transistor is electrically coupled to an RF signal input terminal of the driver stage die, and the integrated portion of the interstage impedance matching circuit is electrically coupled between a current-carrying terminal of the first transistor and an RF signal output terminal of the driver stage die. The second die includes a III-V semiconductor substrate (e.g., a GaN substrate) and a second transistor. A connection, which is a non-integrated portion of the interstage impedance matching circuit, is electrically coupled between the RF signal output terminal of the driver stage die and an RF signal input terminal of the final stage die.

The present disclosure relates to a packaged radiofrequency (RF) power amplifier. The present disclosure further relates to a semiconductor die that is used in such a power amplifier and to an electronic device or system that comprises the semiconductor die and/or power amplifier. According to the disclosure, the semiconductor die comprises a second drain bond assembly arranged spaced apart from the first drain bond assembly and electrically connected thereto, wherein the second drain bond assembly is arranged closer to the input side of the semiconductor die than the first drain bond assembly. The RF power amplifier comprises a first plurality of bondwires which extend between the first drain bond assembly and the output lead, and a second plurality of bondwires which extend from the second drain bond assembly to a first terminal of a grounded capacitor.

The present disclosure relates to a packaged radiofrequency (RF) power amplifier. The present disclosure further relates to a semiconductor die that is used in such a power amplifier and to an electronic device or system that comprises the semiconductor die and/or power amplifier. According to the disclosure, the semiconductor die comprises a second drain bond assembly arranged spaced apart from the first drain bond assembly and electrically connected thereto, wherein the second drain bond assembly is arranged closer to the input side of the semiconductor die than the first drain bond assembly. The RF power amplifier comprises a first plurality of bondwires which extend between the first drain bond assembly and the output lead, and a second plurality of bondwires which extend from the second drain bond assembly to a first terminal of a grounded capacitor.