Cmos Switches For Audio Applications

20 CMOS SWITCHES FOR AUDIO APPLICATIONS T. Giffard When about ten years ago the first analogue CMOS switches and multiplexers reached the audio components market, many audio enthusiasts believed that there was at last an end in sight to the use of expensive relays and other electromechanical elements to control volume and rumble or switch signal sources and functions. Unfortunately, the low speeds, high, non-linear on-resistance and level of crosstalk associated with the new devices soon put an end to these expectations. Over the past few years their quality is claimed to have improved considerably. These claims have been tested in our laboratory through a number of CMOS switches and circuits. We will commence by taking from the numerous parameters of CMOS switches those that are of importance to audio designers, namely: ■ resistance of the closed switch (R., in Q); ■ analogue voltage range (Ua in V); ■ R., as a function of Ua (in 07o); ■ consistency of 12., over a number ...