ANALOG_SWITCH

Published:2009/6/24 3:11:00 Author:May | From:SeekIC

This design takes advantage of the strobed output stage of a CA3140 amplifier. With the strobing capability, the circuit's output voltage can be set to either of the input voltages by grounding one of the control inputs, either A or B.When the strobe input at pin 8 is taken below 1V, that amplifier is disabled. The remaining am-plifier then acts as a unity-gain high-impedance buffer.The 10-kΩ output resistor enables the output voltage to swing down to 20 mV from ground. The Zener-diode clamps and associated resistors connected at the strobe inputs can be omitted for the lowest-cost applications. However, experience has shown that they allow the amplifiers to shrug off the effect of high transient voltages.The circuit is particularly suited to 8-bit microcontroller applications, where the strobe inputs can be driven directly from two open-collector output ports under software control.The use of Schottky diodes for Dl and D2 makes possible an output swing of 2.5 V when the circuit is powered from a 5-V supply.



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