Disclosed is an amplifier circuit for providing an output of at least 100 W, preferably of at least 200 W and most preferably of at least 250 W comprising a field effect transistor. A drain of the field effect transistor is connected with a protective feedback circuit. The protective feedback circuit is arranged to reduce an over-voltage energy at the drain of the field effect transistor if the voltage between the gate and a drain of the field effect transistor exceeds a feedback threshold voltage. Further disclosed is a radio frequency amplifier comprising an amplifier circuit, an electrical radio frequency generator comprising the radio frequency amplifier and a plasma processing system comprising an electrical radio frequency generator. Still further disclosed is a method of protecting a field effect transistor in an amplifier circuit.

An amplifier circuit amplifies a radio-frequency signal. The amplifier circuit includes an amplifier, an input matching circuit connected to an input side of the amplifier and matches impedance, and a protection circuit connected to a node in a path within a path between an input matching circuit and the amplifier. The protection circuit includes a first diode connected between the node and a ground, and a second diode connected in parallel with the first diode and connected in a direction opposite to the first diode between the node and the ground. A threshold voltage of each of the first diode and the second diode is greater than a maximum voltage amplitude of the input signal at the node and is less than a difference between a withstand voltage of the amplifier and the bias voltage.

In a limiting circuit that limits an output voltage of an operational amplifier, the signal quality of the output voltage is improved.

The limiting circuit includes a short-circuit transistor and a gate voltage supply unit. In the limiting circuit, the short-circuit transistor short-circuits a path between an input terminal and an output terminal of the operational amplifier in a case where a voltage between the input terminal of the operational amplifier and the gate is higher than a predetermined threshold voltage. Furthermore, in the limiting circuit, the gate voltage supply unit supplies a voltage to the gate, the voltage depending on the threshold voltage and the output voltage of the output terminal.

An amplification device includes an amplification circuit and a protection circuit. The amplification circuit includes a transistor having a first terminal for outputting an amplified radio frequency signal, a second terminal, and a control terminal coupled to the input terminal of the amplification circuit for receiving a radio frequency signal to be amplified. The protection circuit has a first terminal coupled to the output terminal or the input terminal of the amplification circuit, and a second terminal. The protection circuit includes a switch and a first voltage clamping unit. The switch unit is turned on or turned off according to a control signal. The first voltage clamping unit is coupled to the switch unit for clamping a voltage at the first terminal of the protection circuit within a predetermined region when the switch unit is turned on.

In some embodiments, a power amplification system can comprise a current source configured to provide a bias current, a current mirror configured to mirror the bias current, a comparator configured to compare the mirrored bias current to a threshold current, and a transistor at an output of the comparator. The transistor can be configured to be activated in response to the mirrored bias current exceeding the threshold current.

A circuit for protecting an amplifier includes a detection circuit, a controller and a bypass impedance adjustment circuit. The detection circuit is configured to detect an operation electrical signal of a power amplifier and generate a trigger electrical signal based on the operation electrical signal correspondingly. A first output end of the controller is connected to a base or a gate or a bias circuit of the power amplifier, and a second output end of the controller is connected to a control input end of the bypass impedance adjustment circuit. The bypass impedance adjustment circuit is connected in parallel with the power amplifier. The controller is configured to generate a first control signal and a second control signal based on the trigger electrical signal, and the first control signal is configured to control a bias current or bias voltage of the power amplifier.

A signal processor and method. The signal processor includes a signal current path. The signal processor includes a transconductor. The transconductor has an input operable to receive an input voltage of the signal processor. The transconductor also has an output operable to output a current based on the input voltage. The signal processor also includes a processing stage coupled to the output of the transconductor to receive and process the current outputted by the transconductor. The signal processor further includes a current replicator operable to generate a replica current proportional to the current outputted by the transconductor. The signal processor also includes a comparator operable to compare an output of the current replicator with a reference. The signal processor further includes a current limiter operable to limit the current outputted by the transconductor based on the comparison of the output of the current replicator with the reference.

A circuit element is formed on a substrate made of a compound semiconductor. A bonding pad is disposed on the circuit element so as to at least partially overlap the circuit element. The bonding pad includes a first metal film and a second metal film formed on the first metal film. A metal material of the second metal film has a higher Young's modulus than a metal material of the first metal film.

A power amplifier system having a power amplifier with a signal input and a signal output, bias circuitry coupled to the signal input, and a radio frequency (RF) peak detector having an input coupled to the signal output is disclosed. The RF peak detector is configured to generate a peak voltage signal. Temperature-compensated overvoltage protection circuitry coupled between an output of the RF peak detector and a control input of the bias circuitry is configured to respond to the peak voltage signal crossing over a predetermined peak voltage threshold and to provide an overvoltage protection control signal to cause the bias circuitry to adjust biasing for the power amplifier to reduce an overvoltage condition at the RF peak detector input.

A power amplifier circuit includes a first amplifier that amplifies an input signal and outputs a first amplified signal, a second amplifier that is disposed subsequent to the first amplifier and that amplifies the first amplified signal and outputs a second amplified signal, and a clamp circuit that is disposed between ground and a signal line extending between the first amplifier and the second amplifier and that suppresses an amplitude of the first amplified signal.