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Certain CMOS multiplexers may be protected against overvoltage destruction with diode and resistor networks that shut down any parasitic transistors in the device, limit the current input to a safe level, and shunt input signals to ground when the power supplies are turned off (Circuit A). JFET transistors also protect multiplexer inputs when they are connected as diodes. The JFET clamps at about 0.6 V, protecting the sensitive opamp input from destruction (Circuit B).

Topic: Signal Conditioning Fundamentals