An envelope-tracking current bias circuit includes a first rectifying circuit, a second rectifying circuit, and a first arithmetic circuit. The first rectifying circuit is configured to detect an envelope of an input signal, and provide an envelope detection signal comprising a first direct current (DC) offset voltage. The second rectifying circuit is configured to provide a second DC offset voltage corresponding to the first DC offset voltage. The first arithmetic circuit is configured to provide an envelope signal in which the first DC offset voltage is reduced through subtraction between the envelope detection signal and the second DC offset voltage.

An amplifier circuit includes an input stage, having a positive input end and a negative a negative input end, for generating a pair of differential signals according to a first input voltage received from the positive input end and a second input voltage received from a negative input end; an output stage, coupled to the input stage for generating an output voltage at an output end according to the pair of differential signals; a feedback stage, coupled between the output end and the negative input end; and a clamping unit, coupled between the positive input end and the negative input end for adjusting the second input voltage when the first input voltage is varied so as to clamp a voltage difference between the first input voltage and second input voltage.

An amplifier circuit includes an input stage, having a positive input end and a negative a negative input end, for generating a pair of differential signals according to a first input voltage received from the positive input end and a second input voltage received from a negative input end; an output stage, coupled to the input stage for generating an output voltage at an output end according to the pair of differential signals; a feedback stage, coupled between the output end and the negative input end; and a clamping unit, coupled between the positive input end and the negative input end for adjusting the second input voltage when the first input voltage is varied so as to clamp a voltage difference between the first input voltage and second input voltage.

An envelope-tracking current bias circuit includes a first rectifying circuit, a second rectifying circuit, and a first arithmetic circuit. The first rectifying circuit is configured to detect an envelope of an input signal, and provide an envelope detection signal comprising a first direct current (DC) offset voltage. The second rectifying circuit is configured to provide a second DC offset voltage corresponding to the first DC offset voltage. The first arithmetic circuit is configured to provide an envelope signal in which the first DC offset voltage is reduced through subtraction between the envelope detection signal and the second DC offset voltage.

A circuit can include a first current source, a second current source, and a differential inverter amplifier electrically coupled between the first current source and the second current source. The differential inverter amplifier can include a plurality of load resistors and a plurality of diode-connected metal oxide semiconductor (MOS) clamps configured to limit output swing and minimize common mode disturbances.