A power amplifier includes a two-dimensional matrix of NM active cells formed by stacking main terminals of multiple active cells in series. The stacks are coupled in parallel to form the two-dimensional matrix. The power amplifier includes a driver structure to coordinate the driving of the active cells so that the effective output power of the two-dimensional matrix is approximately NM the output power of each of the active cells.

An operational amplifier includes a gain boost circuit. The gain boost circuit includes a first differential gm amplifier of a first stage, and a second differential gm amplifier of a post stage. Phase compensation capacitors are provided between inputs and outputs of a system of the second differential gm amplifier.

Techniques for monitoring a distortion signal of a power amplifier circuit, where the output of a distortion monitoring circuit includes little or no fundamental signal and closely represents the actual distortion of the amplifier circuit of a wired communications system. The power amplifier circuit can generate a distortion feedback signal that does not affect the power amplifier's output power capability, e.g., no inherent loss in the fundamental output of the amplifier. That is, using a distortion monitor circuit, the power amplifier circuit can resolve a distortion feedback signal from the intended output signal of the output power amplifier circuit.

An operational amplifier based circuit has an operational amplifier, a feedback circuit, and a compensation circuit block. The feedback circuit is coupled between an output port and an input port of the operational amplifier. The compensation circuit block has circuits involved in stability compensation of the operational amplifier, wherein there is no stability compensation circuit driven at the output port of the operational amplifier.

Aspects and examples described herein provide a variable gain amplifier circuit and assembly. In one example, a variable gain amplifier circuit includes a signal input, a signal output, and a variable gain amplifier including a plurality of unit cell groups coupled between the signal input and the signal output, the variable gain amplifier configured to provide an adjustable gain to a signal received at the signal input during each of a plurality of amplify modes of the variable gain amplifier, each of the plurality of amplify modes corresponding to at least one unit cell group of the plurality of unit cell groups. A bypass path including a fixed attenuator is coupled in parallel with the variable gain amplifier between the signal input and the signal output to selectively couple the signal input to the signal output through the fixed attenuator during a bypass mode.

A power amplifier includes a two-dimensional matrix of NM active cells formed by stacking main terminals of multiple active cells in series. The stacks are coupled in parallel to form the two-dimensional matrix. The power amplifier includes a driver structure to coordinate the driving of the active cells so that the effective output power of the two-dimensional matrix is approximately NM the output power of each of the active cells.