multiplexer switch circuit diagram

Multiplexer Switch Circuit with 4066

This multiplexer switch circuit is built with the IC 4066 and was designed to switch multiple signal sources into a single common output and can be used as a replacement for the conventional mechanical switches.
Conventional multiplexer switches hava an annoying disadvantage that the video signals mix over when the source is changed but this circuit avoids this problem by disabling the inactive signal line.

The heart of the switch is a digitally controlled analog switch 4066. The switches are ES1 … ES8 and each 4066 contains 4 switches. When channel 1 is selected, ES1 and ES2 are closed and ES3 is open. Channel is suppressed at this moment since ES5 and ES6 are open and ES7 prevents cross-over between the two channels by grounding the channel 2 line.

The bandwidth of the multiplexer sw circuit is around 8 MHz. The current consumption is 1 mA. A high level power supply voltage level is required since the input impedance level of the circuit drops with higher voltage levels.

When the multiplexer circuit is connected to a 75 Ω impedance load, some signal losses will result due to the internal resistance of the switches. This can be compensated by connecting a video amplifier at the output.
Article submitted by Michael Gregory – Romania.

Multiplexer Switch Circuit Diagram

multiplexer switch circuit diagram

One Comments

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  • Maxthon Chan

    It seem to me that this circuit is a little bit too complicated and cannot handle signals well due to high resistance of 4066s. I’d suggest adding op-amp buffers at inputs and outputs, and feed input signals to the output single-endedly (like open-drain logic) with a pull-down resistor.

    First, raise the input signal to 1/2Vdd after an AC coupling. buffer the input with op-amp voltage follower. Now the switching 4066s come in, all inputs go through one switch and then connected together, with a pull-down resistor. Then an op-amp with an adjustable gain as its output.

    Using this design, you can build a stereo one out of one LM324 quad op-amp (input buffers), one CD4066 quad analog switch, two resistors, one LM358 dual op-amp (output buffers) and a double-action pot (to adjust gain. You can omit it so the output is a simple DC buffer, or use some resistors so that the output have a constant gain.) Both inputs can be switched on or off independently, and if you need to control it with one input a transistor inverter (or if you dare to use SMT parts, a 74HC1G04) can be used to link the two control lines.

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