Apparatus and methods for bias switching of power amplifiers are provided herein. In certain configurations, a power amplifier system includes a power amplifier that provides amplification to a radio frequency (RF) signal and a bias control circuit that biases the power amplifier. The power amplifier includes an amplification transistor that receives the RF signal at an input, and a first bias network and a second bias network each connected to the input. The bias control circuit includes a first switch, a first reference current source that provides the first reference current to the first bias network through the first switch, a second switch, and a second reference current source that provides the second reference current to the second bias network through the second switch.

Apparatus and methods for bias switching of power amplifiers are provided herein. In certain configurations, a power amplifier system includes a power amplifier that provides amplification to a radio frequency (RF) signal and a bias control circuit that biases the power amplifier. The power amplifier includes an amplification transistor that receives the RF signal at an input, and a first bias network and a second bias network each connected to the input. The bias control circuit includes a first switch, a first reference current source that provides the first reference current to the first bias network through the first switch, a second switch, and a second reference current source that provides the second reference current to the second bias network through the second switch.

A phase shift circuitry includes: a signal generation circuitry that receives an input signal, and outputs four signals different in phase from each other by 90 degrees based on the input signal, the four signals includes a first signal and a second signal; four variable amplifier circuitry that each includes a transistor, and amplify the four signals individually, with amplification factors based on control voltages supplied to gates of the transistors, the four variable amplifier circuitry include a first amplifier amplifies the first signal by a first control voltage and a second amplifier amplifies the second signal by a second control voltage; a synthetic circuitry that synthesizes output signals of the four variable amplifier circuitry, and outputs a synthesized signal; and a control circuitry supplies voltages, that are equal to or higher than the gate threshold value, to the first amplifier and the second amplifier.

A phase shift circuitry includes: a signal generation circuitry that receives an input signal, and outputs four signals different in phase from each other by 90 degrees based on the input signal, the four signals includes a first signal and a second signal; four variable amplifier circuitry that each includes a transistor, and amplify the four signals individually, with amplification factors based on control voltages supplied to gates of the transistors, the four variable amplifier circuitry include a first amplifier amplifies the first signal by a first control voltage and a second amplifier amplifies the second signal by a second control voltage; a synthetic circuitry that synthesizes output signals of the four variable amplifier circuitry, and outputs a synthesized signal; and a control circuitry supplies voltages, that are equal to or higher than the gate threshold value, to the first amplifier and the second amplifier.

One example includes an amplifier system. The amplifier system includes an input stage configured to receive an input pulse signal and to generate a reference voltage pulse based on the input pulse signal. The amplifier system also includes an amplifier stage that receives at least one power voltage and is configured to amplify the reference voltage pulse and to provide pulse-shaping of the amplified reference voltage pulse based on a change of amplitude of the at least one power voltage resulting from an amplitude of the reference voltage pulse.

One example includes an amplifier system. The amplifier system includes an input stage configured to receive an input pulse signal and to generate a reference voltage pulse based on the input pulse signal. The amplifier system also includes an amplifier stage that receives at least one power voltage and is configured to amplify the reference voltage pulse and to provide pulse-shaping of the amplified reference voltage pulse based on a change of amplitude of the at least one power voltage resulting from an amplitude of the reference voltage pulse.

An RF amplifier to increase a gain using a transformer is provided. The amplifier includes: a first transistor configured to generate a current by amplifying and converting an input voltage; a second transistor configured to amplify the generated current; and a first transformer configured to feed an emitter current of the second transistor back to a gate. Accordingly, G.sub.m of the transistor is boosted using the transformer, such that a high gain can be obtained with a low current. Therefore, a problem of a gain reduction caused by a parasitic capacitor at a high frequency can be solved.

An RF amplifier to increase a gain using a transformer is provided. The amplifier includes: a first transistor configured to generate a current by amplifying and converting an input voltage; a second transistor configured to amplify the generated current; and a first transformer configured to feed an emitter current of the second transistor back to a gate. Accordingly, G.sub.m of the transistor is boosted using the transformer, such that a high gain can be obtained with a low current. Therefore, a problem of a gain reduction caused by a parasitic capacitor at a high frequency can be solved.

A gate bias circuit for a plurality of GaAs amplifier stages is a transistor coupled to a temperature compensation current received from a CMOS control stage. A plurality of pHEMPT amplifier stages are coupled to the gate bias circuit and to a control voltage which switches the amplifier stage. A selectively controlled stage pass transistor enables a current mirror between the gate bias circuit and each stage amplifying transistor. The penultimate pHEMPT amplifier stage is coupled to a CMOS amplifier. A CMOS circuit provides both the temperature compensation current by a proportional to absolute temperature (PTAT) circuit and the control voltage enabling each pHEMPT transistor to receive its input signal in combination with the gate bias voltage.

A gate bias circuit for a plurality of GaAs amplifier stages is a transistor coupled to a temperature compensation current received from a CMOS control stage. A plurality of pHEMPT amplifier stages are coupled to the gate bias circuit and to a control voltage which switches the amplifier stage. A selectively controlled stage pass transistor enables a current mirror between the gate bias circuit and each stage amplifying transistor. The penultimate pHEMPT amplifier stage is coupled to a CMOS amplifier. A CMOS circuit provides both the temperature compensation current by a proportional to absolute temperature (PTAT) circuit and the control voltage enabling each pHEMPT transistor to receive its input signal in combination with the gate bias voltage.