Semiconductor device for signal amplification

The semiconductor device for signal amplification according to claim 1 further comprising:na current source circuit operable to generate a constant current unchangeable in temperature and to supply the constant current to the first transconductance amplifier stages so as to specify operating current of the first transconductance amplifier stages;a modulator circuit with a gain adjustable by a control signal, the modulator circuit operable to modulate a baseband signal to produce a modulated signal and to supply the modulated signal concerned to the ladder network as the input signal;a replica modulator circuit having the same structure as the modulator circuit, being coupled fixedly with a coupling path of a switching stage, having a gain adjustable by the control signal, and operable to modulate a first voltage with a fixed voltage level in simulation;at least one of replica amplifier having the same structure as the first transconductance amplifier stages and being operable to generate a signal corresponding to an output signal of the replica modulator circuit; anda differential amplifier circuit operable to generate the control signal by amplifying differentially the output signal of the replica amplifier and a second fixed voltage.

The semiconductor device for signal amplification according to claim 1,nwherein the ladder network includes:a plurality of first impedance components coupled in series to the input node receiving the input signal; anda plurality of second impedance components arranged corresponding to the first impedance components and coupled to the corresponding first impedance component in parallel,wherein each of the second impedance components has a first sub impedance component and a second sub impedance component coupled in series, andwherein each transconductance amplifier stage receives a signal at a connection node between the corresponding first sub impedance component and the corresponding second sub impedance component.

The semiconductor device for signal amplification according to claim 1 further comprising:nat least one of second transconductance amplifier stage coupled to the input node and enabled selectively according to the control word, and in an enabled state, operable to transmit a current corresponding to an input signal at the input node to the output signal line,wherein the second transconductance amplifier stage has different transconductance from the first transconductance amplifier stage.