Making opamp output open circuit

Hayato said:

You didn't found any Multiplexer. You found a lot of ADCs, R/D convertors... But any Multiplexers.

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Opps, I'm sorry, I pasted the wrong page URL. I checked for multiplexers too, they where also expensive.

dougy83 said:

Maybe check the datasheet for that.

They're supposed to exhibit a pretty good transfer characteristic of a resistor. I do know that most have a varying resistance depending on the voltage passed - so as long as they're driving a high impedance device, there should not be any issues.

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It is good to hear, the worst case is that if the signal is distorted or clipped. If the signal is linearly transfered, there is no problem for me.

crutschow said:

Three important characteristics of analog multiplexers to note are: on-resistance, signal amplitude for normal operation, and switching speed. These are noted in the multiplexer data sheet.

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Great information, thank you very much.

Roff said:

You also need to at least consider parasitic capacitances.

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I will consider that, thank you.

Mikebits said:

Here is an opamp with output disable pin. https://www.electro-tech-online.com/custompdfs/2010/01/LMH6732-1.pdf

You might be able to get a sample from national.

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I think I decided to use analog multiplexer instead of an opamp, thank you anyway.

Roff said:

Intersil makes a 4 channel selectable op amp, the **broken link removed**. They are expensive (US $15.76 from Intersil).

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That's too expensive for my project. But one day I may need it for another project. I will keep its datasheet. Thank you.

dougy83 said:

I get the feeling the OP is happy to use an analogue MUX now that he knows they are dirt cheap.

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You bet!

dougy83 said:

I get the feeling the OP is happy to use an analogue MUX now that he knows they are dirt cheap.

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It is always good to have options.

Hi there,


Analog multiplexers do have some specs you have to look over.
On resistance, leakage, max frequency, max switching, crosstalk, and clock punch through to name a few.
The on resistance and max specs can vary with power supply voltage, and clock punch through can cause annoying clicks sometimes.
The clock problem can sometimes be diminished greatly by using dual differential channels, if it really does cause a problem in
the application.
Some switches are made better than others too with better specs, but are more expensive. The cheapest seems to be the CMOS variety.

hkBattousai said:

I read datasheet of 405x family (x=1,2,3), There is no clear indication about this matter. I am new to this analog multiplexer thing, I don't even know their working principles.

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http://www.geofex.com/article_folders/cd4053/cd4053.htm