A high-speed, high-voltage gallium nitride based (GaN-based) operational amplifier (op amp) is disclosed. The combined high-speed, high-voltage capability allows the GaN-based op amp to serve as a dynamic power supply (DPS) for a radio frequency power amplifier (RFPA). When serving as a DPS for an RFPA, the GaN-based op amp is capable of supplying ampere-scale currents that accurately track rapidly-varying envelopes of non-constant envelope RF signals, thereby allowing the RFPA to convert high-bandwidth non-constant envelope RF signals to high RF output powers with high signal envelope accuracy.

A differential operational amplifier, which comprises: a voltage adjusting module, coupled between a first predetermined voltage source and a second predetermined voltage source, for adjusting a first voltage via a first voltage adjusting value to generate a first adjusted voltage, and for adjusting a second voltage via a second voltage adjusting value to generate a second adjusted voltage, wherein the first voltage adjusting value and the second voltage adjusting value change corresponding to a temperature; and a differential signal computing module, coupled between the first predetermined voltage source and the second predetermined voltage source, for generating an output voltage according the first adjusted voltage and the second adjusted voltage.

A differential MEMS-readout circuit comprises a first input bonding pad, including a first contact pin and a second contact pin. The differential MEMS-readout circuit comprises a second input bonding pad, including a first contact pin and a second contact pin; and a differential-readout amplifier section comprising a first input connected to the first contact pin of the first input bonding pad and a second input connected to the first contact pin of the second bonding pad, wherein the differential-readout amplifier section comprises a first and a second transistor circuit and each of the second contact pins of the first and second input bonding pads is coupled to one of the first and the second transistor circuits or is coupled to one of the first and the second transistor circuits and/or to ground.

An operational amplifier includes a first power voltage end, a second power voltage end, a first-stage operational amplification circuit, and a second-stage operational amplification circuit. The first power voltage end is configured to receive a first power voltage signal, the second power voltage end is configured to receive a second power voltage signal, and a voltage value of the first power voltage signal is greater than a voltage value of the second power voltage signal. The first-stage operational amplification circuit is configured to receive an input signal via a signal input end, and amplify the input signal under enabling control of the first power voltage signal, to generate a first drive signal. The second-stage operational amplification circuit is configured to generate an output signal.