A signal amplifier device is provided to ensure the continuity of the gain of an amplifier. The signal amplifier device includes a main path and a sub path connected in parallel to the main path. A main path first amplifier circuit amplifies an input signal on the main path. A main path second amplifier circuit includes a common-gate transistor connected in series with an output of the main path first amplifier circuit without sharing a DC current. On the main sub path, the sub path amplifier circuit amplifies the input signal by using a gain lower than the maximum gain in the main path.

A signal amplifier device is provided to ensure the continuity of the gain of an amplifier. The signal amplifier device includes a main path and a sub path connected in parallel to the main path. A main path first amplifier circuit amplifies an input signal on the main path. A main path second amplifier circuit includes a common-gate transistor connected in series with an output of the main path first amplifier circuit without sharing a DC current. On the main sub path, the sub path amplifier circuit amplifies the input signal by using a gain lower than the maximum gain in the main path.

In certain aspects, an apparatus includes a transformer including an input inductor and an output inductor, wherein the input inductor is magnetically coupled to the output inductor. The apparatus also includes a transconductance driver configured to drive the input inductor based on an input signal. The apparatus further includes a feedback circuit configured to detect an output voltage swing at the output inductor, generate a regulated voltage at the input inductor, and control the regulated voltage based on the detected output voltage swing.

In certain aspects, an apparatus includes a transformer including an input inductor and an output inductor, wherein the input inductor is magnetically coupled to the output inductor. The apparatus also includes a transconductance driver configured to drive the input inductor based on an input signal. The apparatus further includes a feedback circuit configured to detect an output voltage swing at the output inductor, generate a regulated voltage at the input inductor, and control the regulated voltage based on the detected output voltage swing.

A compensation circuit comprising: a first source having an output; a second source having an output; a first transistor having a first current terminal coupled to the output of the first source, a second current terminal coupled to ground and a first control terminal connected to the first current terminal; a second transistor having a second control terminal, a third current terminal coupled to the output of the second source and a fourth current terminal coupled to ground; a first resistor connected between the first control terminal and the second control terminal; and a capacitor having a first terminal and a second terminal, the first terminal of the capacitor connected to the second control terminal.

Low noise voltage generation circuitry includes a voltage source, a low-pass filter with one or more filter stages, and an amplifier selectively coupled to the filter stages. Each filter stage includes a resistor and a pair of capacitors of equal capacitance. The amplifier has an input selectively coupled to an output port of the voltage generation circuitry and has an output selectively coupled to the pair of capacitors in each filter stage. During a sensing phase, the amplifier senses the voltage at the output port. During a first charging phase, the amplifier has a first polarity and charges one of the pair of capacitors in each filter stage. During a second charging phase, the amplifier has a second polarity and charges another one of the pair of capacitors in each filter stage. During a final phase, the pair of capacitors within each filter stage are shorted together to cancel out an amplifier offset while the output port instantaneously settles to the target voltage.

One aspect of this disclosure is a power amplifier system that includes a control interface, a power amplifier, a passive component on a same die as the power amplifier, and a bias circuit on a different die than the power amplifier. The control interface can operate as a serial interface or as a general purpose input/output interface. The power amplifier can be controllable based at least partly on an output signal from the control interface. The bias circuit can generate a bias signal based at least partly on an indication of the electrical property of the passive component. Other embodiments of the system are provided along with related methods and components thereof.

[Proposed] is an activation circuit which can realize both of area reduction and current consumption reduction by more preferred embodiments. [Solution] An activation circuit has: an N-type MOS transistor having a gate terminal connected to a ground and having a threshold voltage in a vicinity of 0 V; and a resistor interposed between a source terminal of the MOS transistor and a ground, wherein an electric potential of a drain terminal of the MOS transistor is controlled depending on a first signal output from a device serving as a drive target, and transmission of a second signal for activating the device is controlled depending on the electric potential of the drain terminal.

A measurement circuit may include a transistor having a first terminal, a second terminal, and a third terminal, wherein the first terminal is coupled to a first reference voltage. The measurement circuit may further include a first operational amplifier including a first input coupled to the second terminal of the transistor and an output coupled to the third terminal of the transistor. The first operational amplifier may further include a second input configured to receive a second reference voltage. The measurement circuit may also include a first unity-gain voltage follower including a second operational amplifier having a first input coupled to the first input of the first operational amplifier. Methods of measuring a threshold voltage, semiconductor devices, and electronic systems are also described.

An input circuit includes an input stage having an input node and a direct-current (DC) amplifier coupled to the input node. The input circuit also includes an alternating-current (AC) amplifier coupled to an output node of the DC amplifier. The input circuit also includes a capacitor coupled between the input node and the output node of the DC amplifier. The input circuit also includes a voltage divider coupled to the DC amplifier and the AC amplifier. The voltage divider includes first resistor associated with the DC amplifier and a second resistor associated with the AC amplifier, where the first resistor is larger than the second resistor.