| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high voltage analog switching circuit with a small ON resistance that is not destroyed even when a high voltage is applied to the input or output. SOLUTION: The analog switching circuit is configured with Nch-MOS transistors(TRs) 2a, 2b with a high drain-source breakdown voltage BVDS, a low gate-source breakdown voltage BVGS and a low threshold voltage VT and with a Pch-MOS TR 2c with high BVDS and BVGS. Nch-MOS TRs 2e, 2d with high BVDS and BVGS are connected to an inter-source connecting point 2S between the Nch-MOS TRs 2a, 2b. A high voltage is applied to input output terminals IN/OUT21, 22, and even when a very small leakage exists between the drain and source (D.S) terminals of the Nch-MOS TRs 2a, 2b and the voltage of the terminals is to increase, since the Nch-MOS TRs 2a, 2b are conductive, the level of the inter-source connecting point 2S is fixed to a VDD1 and a voltage over the BVGS is not applied between the gate and source (G.S) of the Nch-MOS TRs 2a, 2b.
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