Electronics > Beginners

Exponential Amplifier

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exe:

--- 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.

eev_carl:

--- 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 ---

What do you think about the anti-log schematics in the TI links posted above?  Are you suggesting that the diode should be replaced with a BJT?

Alex Nikitin:

--- Quote from: eev_carl on July 25, 2018, 01:21:05 pm ---Hi,

I built the exponential amp w. a single diode. Here is my schematic


--- End quote ---

 :palm: :palm:

Your schematics is wrong. It is not what you've built and measured.

Cheers

Alex

eev_carl:

--- Quote ---Your schematics is wrong. It is not what you've built and measured.
--- End quote ---

That's my bad Eagle skills...fixing + to ground

(replaced incorrect Eagle schematic with handdrawn schematic showing the inverting amp)

exe:

--- Quote from: eev_carl on July 25, 2018, 01:33:15 pm ---What do you think about the anti-log schematics in the TI links posted above?  Are you suggesting that the diode should be replaced with a BJT?

--- End quote ---

Ah, now I see the updated schematics :). I'd say, if diode works for you, then don't make your life harder with more complicated circuits. Just know limitations of your solution (mainly thermal drift).

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