What I’d stumbled upon was a chopper amplifier, a slightly ungainly and long superseded solution to the problem of DC amplification from the days before ubiquitous integrated circuit op-amps.

The operational amplifier, or op amp, is one of the most basic building blocks used in analog circuits. Ever since single-chip op amps were introduced in the 1960s, thousands of different types ...

and MOSFETs), and the frequency response of transistors for single-stage and multi-stage amplifiers. To make use of the versatility of op-amps we normally use them connected in negative feedback. When ...

This pocket-sized headphone amplifier works with wired and wireless headphones and includes Qualcomm's flagship Bluetooth ...