Analog switch circuit and signal attenuator employing an analog switch circuit

摘要

An analog switch circuit comprises a first transfer gate (20) and a second transfer gate (23). The first transfer gate comprise first P-type and N-type field-effect transistors (21) and (22) having first electrodes thereof commonly connected through an output terminal (5) to a load (6) and second electrodes thereof commonly connected through an input terminal (4) to an input signal source (7) of an impedance lower than that of the load. The second transfer gate comprises second P-type and N-type field-effect transistors (24) and (25) of a gate size smaller than that of the respective transistors constituting the first transfer gate having the first and second electrodes connected in parallel with the first and second electrodes of the first P-type and N-type transistors, respectively. The second transfer gate is first turned on and then the first transfer gate is turned on, whereby a switching noise on the occasion of turning on of the first transfer gate is bypassed through the second transfer gate to the input signal source.