Electronic – Analog buffer without op-amps


I need to buffer an input signal such that I do not load down the source, which is a 100k resistor. However, I need to buffer at least 6 channels, and for more advanced models I'd like to move to 10 channels (for the more advanced one I'd be okay using multiple chips though.)

I'd rather not use op-amps, because they will take up considerable space – just wiring the inverting or noninverting to the output, for example, uses a lot of space for traces – also, half the pins would be unneeded.

I'm not sure what chip or type of chip to be looking for – all the buffers I've found so far only work for digital logic, not analog signals. The buffer should have very low input bias current (nanoamps to hundreds of picoamps), like a JFET op-amp.

Best Answer

It seems after some discussion that you are looking for a buffer amplifier.

Digikey has a section for this. if you go to the main area for linear amplifiers and then select for buffer type and in stock you get quite a list. I selected for those with an input current of 2nA typical I got a relatively short list(like 10). This however does not give me an easy way to share the links, so you will have to click it yourself.

These are designed to give you the features you want and in a small package, now they normally come in groups of 2^n, so you will have to get a package of 8, but I am sure you can make it work.

Markrages had a bit of extra input to add in a comment:

Cautions about those buffer amps: Most of them are made for video signals and so they are high bandwidth / high current designs. That's a consideration if the circuit is battery powered. Also note that (the ones I looked at) are specialized, single vendor parts. More expensive and more availability risk than op-amps or transistors with standardized footprints. Engineers have a duty to only use oddball parts when their special features are necessary and relevant to the design.