Differential amplifier circuitry including: first and second main transistors of a given conductivity type; and first and second auxiliary transistors of an opposite conductivity type, where the first and second main transistors are connected along first and second main current paths passing between first and second main voltage reference nodes and first and second output nodes, respectively, with their source terminals connected to the first and second output nodes, respectively, and with their gate terminals controlled by component input signals of a differential input signal; and the first and second auxiliary transistors are connected along first and second auxiliary current paths passing between first and second auxiliary voltage reference nodes and the first and second output nodes, respectively, with their drain terminals connected to the first and second output nodes, respectively, and with their gate terminals controlled by the component input signals of the differential input signal.

A programmable gain amplifier that comprises: a transconductance amplifier, a switch leakage compensation circuit and a transimpedance amplifier. The transconductance amplifier provides a transconductance amplifier current signal and includes a switchable resistance network. The switch leakage compensation circuit provides a compensation current signal and comprises a switchable compensation resistance network. The transimpedance amplifier provides the output voltage signal based on the difference between the transconductance amplifier current signal and the compensation current signal. The switchable compensation resistance network comprises a plurality of branches in parallel with each other, wherein each branch includes: a gain-mimicking switch that has a corresponding gain-setting switch in the switchable resistance network; and a leakage-current-conducting switch in series with the gain-mimicking switch. The leakage-current-conducting switch is openable and closable in accordance with the complement of a switch control signal that is used to control the gain-mimicking switch in the same branch.

A testing system includes: a dividing circuit configured to receive a testing signal and provide a plurality of input signals according to the testing signal; and a plurality of power-amplifier chips coupled to the dividing circuit, each of the plurality of power-amplifier chips being configured to be tested by receiving a respective input signal of the plurality of input signals and generating a respective output signal for a predetermined testing time.

An operational amplifier includes a first amplifying unit, a second amplifying unit, a current source, a first compensation capacitor, and a second compensation capacitor. The first amplifying unit includes a first input transistor, a second input transistor, a third input transistor, and a fourth input transistor. The second amplifying unit includes a fifth input transistor, a sixth input transistor, a seventh input transistor, and an eighth input transistor. One end of the first compensation capacitor is coupled to a drain of the seventh input transistor, and the other end of the first compensation capacitor is coupled to a gate of the eighth input transistor. One end of the second compensation capacitor is coupled to a drain of the eighth input transistor, and the other end of the second compensation capacitor is coupled to a gate of the seventh input transistor.

The disclosure provides an LDO voltage regulator circuit and a related method. The circuit includes an error amplifier having a localized common-mode feedback circuit, receiving a reference voltage, a feedback voltage, and an input voltage, and generating an amplified error voltage; a pass element having a power transistor, receiving the amplified error voltage, and generating an output voltage; a feedback circuit receiving the output voltage and having a voltage divider which scales down the output voltage; a first compensation element having a first terminal which connects to an output of the input differential transistor pair and a second terminal which receives the output voltage; and a second compensation element having a third terminal which receives the output voltage and connects to the second terminal and a fourth terminal which connects to an input of a first transistor pair of the localized common-mode feedback circuit.

Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can have a varying supply voltage that varies according to a control voltage. The control voltage can be related to a desired output power of the amplifier and/or to an envelope signal of an input signal to the amplifier. Particular biasing for selectively controlling the stacked transistors to operate in either a saturation region or a triode region is also presented. Benefits of such controlling, including increased linear response of an output power of the amplifier, are also discussed.

Various envelope tracking amplifiers are presented that can be switched between an ET (envelope tracking) mode and a non-ET mode. Switches and/or tunable components are utilized in constructing the envelope tracking amplifiers that can be switched between the ET mode and the non-ET mode.

Systems and method for improving operation of a radio frequency system are provided. One embodiment includes a switching power amplifier that outputs an amplified analog electrical signal based on an input electrical signal and voltage of an envelope voltage supply rail. The switching power amplifier includes a first transistor with a gate that receives the input electrical signal, a source electrically coupled to the envelope voltage supply rail, and a drain electrically coupled to an output of the switching power amplifier; a second transistor with a gate that receives the input electrical signal, a source electrically coupled to ground, and a drain electrically coupled to the output; and a third transistor with a gate that receives the input electrical signal, a drain electrically coupled to the envelope voltage supply rail, and a source electrically coupled to an output of another switching power amplifier.

An integrated circuit and method for providing a variable gain amplifier are disclosed. One embodiment of the a variable gain amplifier comprises at least one load, a cascode circuit coupled to the load, a folded-gilbert stage, coupled to the cascode circuit, the folded-gilbert stage comprising a main differential pair of transistors and an internal pair of transistors, and a digital to analog converter, coupled to the folded-gilbert stage, for steering currents between the main differential pair of transistors and the internal pair of transistors to change a gain of the variable gain amplifier.

A driver that drives an optical device, such as laser diode (LD) and/or optical modulator, is disclosed. The driver includes a variable gain amplifier (VGA) and a post amplifier. The post amplifier amplifies an output of the VGA to a preset amplifier as varying the gain of the VGA. The VGA includes two differential pairs each amplify the input signal oppositely in phases thereof and outputs of the differential pairs are compositely provided to the post amplifier. The gain of the VGA is varied by adjusting contribution of the second differential pair to the output of the VGA.