A power amplifier comprising a first member and a second member including a compound semiconductor region joined to a first face of the first member including a semiconductor region. The second member includes an amplifier circuit including a compound semiconductor element, and multiple clamp diodes connected in multiple stages and between an output port of the amplifier circuit and ground. The first member includes a switch, connected between an extension point, which is a middle point of the multiple clamp diodes and the ground, a temperature sensor, and a switch control circuit which performs on-off control of the switch based on a result of measurement by the temperature sensor. The extension point is connected to the switch via a path including an inter-member connection wire on an interlayer insulating film from the first face of the first member to a surface of the second member.

Subsystems and methods disclosed herein provide a reference signal to a power amplifier (PA) of an RF transmitter or transceiver. PTAT and CTAT signals and a temperature indication signal are produced. Based on the temperature indication signal, one of the PTAT or CTAT signals is selected to be used to produce one or more DAC reference signals. Using the selected one of the PTAT or CTAT signals, the one or more DAC reference signals are produced and used to bias the DAC. A multi-bit digital input signal is converted to an analog output signal using the DAC that is biased using the one or more DAC reference signals (produced using the selected one of the PTAT or CTAT signals). Further, the analog signal output by the DAC, or an amplified version thereof, is used as the reference signal that is provided to the PA of the RF transmitter or transceiver.

Methods related to power amplification systems with adjustable common base bias. A method of implementing a power amplification system can include providing a cascode amplifier coupled to a radio-frequency input signal and coupled to a radio-frequency output. The method can further include providing a biasing component configured to apply one or more biasing signals to the cascode amplifier, the biasing component including a bias controller and one or more bias components. Each respective bias component may be coupled to a respective bias transistor.

One embodiment is a lower power technique to compensate for radio frequency (RF) amplifier gain and phase over temperature and part-to-part variation for particular use in phased array (PA) applications.

A power amplifier with clamp and feedback protection circuitry is disclosed. In one aspect, the power amplifier is initially protected by a fast-acting clamp circuit whose overall size is relatively limited. Subsequent operation allows a comparatively slowly acting feedback loop to dominate the protection of the power amplifier. By providing the two protection circuits, each optimized for a particular phase of protection, the overall size of associated protection circuitry may be diminished while still protecting the power amplifier from failure inducing conditions.

Examples of amplifier circuitry regulate a transconductance value (G.sub.m) of operational transconductance amplifiers (OTAs) in the amplifier to be approximately the same, which value is based on a supply voltage and a reference voltage applied to a reference OTA and the internal resistance of the reference OTA. The reference OTA generates an output current based on G.sub.m and the reference voltage, which current is compared to current generated by the supply voltage and internal resistance of the reference OTA. A tail current transistor of each of the reference OTA and a main OTA that mirrors the G.sub.m of the reference OTA provide a tail current feedback path by which G.sub.m is regulated. Amplifying circuitry is coupled to the main OTA to receive current signals. Based on the received current signals, amplifying circuitry generates a differential output voltage signal. The gain of the amplifying circuitry is proportional to the supply voltage and remains relatively constant across process temperature variations.

A reference voltage generating circuit includes: an operational amplifier including a first input terminal connected to a first node and a second input terminal connected to a second node; a first transistor connected between a ground terminal and the first node, wherein a first current flows in the first transistor; a second transistor connected to the ground terminal; and a first variable resistor connected between the second transistor and the second node, wherein the first variable resistor has a first resistance value for adjusting the first current, based on a change in a current characteristic of the first transistor caused by a variation in a process of forming the first transistor. The reference voltage generating circuit provides a reference voltage, based on a voltage of the first node and a voltage across the first variable resistor.

Provided is a temperature detection circuit that includes: a series connection circuit that is connected between a power supply voltage input terminal and ground and includes a temperature detection transistor and a first resistance element; and a current bypass circuit that includes a first transistor that is connected in parallel with the temperature detection element and allows a bypass current to flow therethrough. The temperature detection circuit outputs a temperature detection signal from a connection point between the temperature detection transistor and the first resistance element.

An amplifier circuit includes an input terminal to which a radio frequency signal is input, an amplifier transistor that has a control terminal and amplifies the radio frequency signal, a bias circuit that includes an emitter-follower circuit or a source-follower circuit and supplies a bias current to the control terminal of the amplifier transistor, an inductor arranged in series between an emitter of the emitter-follower circuit and the control terminal of the amplifier transistor or between a source of the source-follower circuit and the control terminal of the amplifier transistor, and a variable resistance circuit connected to the inductor.

Thermal temperature sensors for power amplifiers are provided herein. In certain implementations, a semiconductor die includes a compound semiconductor substrate, and a power amplifier including a plurality of field-effect transistors (FETs) configured to amplify a radio frequency (RF) signal. The plurality of FETs are arranged on the compound semiconductor substrate as a transistor array. The semiconductor die further includes a semiconductor resistor configured to generate a signal indicative of a temperature of the transistor array. The semiconductor resistor is located adjacent to one end of the transistor array.