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I have two analog signals with frequencies up to 8kHz. I need to select one of the signals using a digital logic select. How can I do this? I need the most reliable IC as our system demands the highest reliability.

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  • \$\begingroup\$ What's the voltage swing? Do you need DC coupling or AC coupling? What sort of source and load impedances are we talking about here? \$\endgroup\$ – alex.forencich May 15 '15 at 5:57
  • \$\begingroup\$ Analog muxing/switching devices are available as COTS devices. Quick search of the internet shows a variety of parts, some up in the GHz range of bandwidth. \$\endgroup\$ – Kris Bahnsen May 15 '15 at 5:59
  • \$\begingroup\$ The signals are coming from a DC/DC converter output.It gives a 3.3 V output to power a micro-controller. \$\endgroup\$ – Naveen May 15 '15 at 8:24
  • \$\begingroup\$ Since you are apparently trying to switch a power supply, you need to tell us how much current will be drawn, and how much voltage drop is allowed across the multiplexer. Also, how fast does the switching process need to be? \$\endgroup\$ – WhatRoughBeast May 15 '15 at 13:12
  • \$\begingroup\$ around 40mAmps current will be drawn and very less voltage drop is allowed .. may be around 100mV \$\endgroup\$ – Naveen May 15 '15 at 15:13
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You can use a SPDT analog switch for this.

The Fairchild FSA5157 is a single-supply SPDT switch with a range of 0 to +V, where the supply voltage (V) can be from 1.8v to 3.3v. The maximum on resistance is 0.7 Ω. It is rated for a continuous switched current of 350 mA.

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The FSA5157 is available from Digi-Key for $0.78 in single quantities

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  • \$\begingroup\$ The signals are coming from a DC/DC converter output.It gives a +3.3 V output to power a micro-controller \$\endgroup\$ – Naveen May 15 '15 at 8:25
  • \$\begingroup\$ @student I updated my answer to include a single supply switch. I left the dual supply in for reference. \$\endgroup\$ – tcrosley May 15 '15 at 8:43
  • \$\begingroup\$ @student I just saw the updates to your requirements. The previous analog switches I had chosen were only rated for 10 mA. This one can carry 350 mA. With a current of 40 mA, and an on resistance of 0.7 Ω, the voltage drop will be in the order of 30 mV. \$\endgroup\$ – tcrosley May 16 '15 at 2:05

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