Electronics > Beginners
Exponential Amplifier
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David Hess:

--- Quote from: exe on July 25, 2018, 01:29:08 pm ---
--- Quote from: eev_carl on July 25, 2018, 01:21:05 pm ---Here is my schematic and test results.
--- End quote ---

Imho this can't work. But even if does, it's just wrong. Diode is biased only by opamp's parasitic input current, that's not how to build circuits.
--- End quote ---

It will work fine and I have done it this way many times in uncritical applications.  The input bias current of the operational amplifier limits accuracy at low currents but so does the diode's leakage which can be considerable if a gold doped switching diode like the 1N4148 is used.

A transistor offers much better dynamic range but most applications do not require it.
eev_carl:

--- Quote ---Imho this can't work
--- End quote ---

This might have referred to a bogus Eagle schematic I put up with the terminals of the op amp mixed up.  My handdrawn schematic is what I have on the breadboard.
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