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opamp and ogarithmic scale

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bizoo

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how can an opamp cicruit be devised to give us a logarithmic output of our input


also how can one desgn a circuit iwth opamps which gives product of two inputs
 

The simplest logarithmic amplifier is one with a diode connected between output (anode) and inverting input(cathode) and the input voltage is fed through a resistor to (-) input. It takes advantage of the expotential dependence of diode current on voltage to take the logarithm of its input signal.
But it is not perfect and very temperature dependant.

Much better circuit with its full description you can find here:
**broken link removed**

Regards,
IanP
 

wat abt the circuit of the products?
 

wat abt the circuit of the products?
Click to expand...
Multipliation?, an opamp can't do this..
You have to go for specialized ICs, such as for example AD534 .. **broken link removed**
Regards,
IanP
 

also one can get the logarithmic out put by having a diode (in reverse bias )in the feedback of opamp,
 

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