i have an urgent question about natural log op-amp circuit

[mick83]

i am given a model 741 op-amp and any resistors and diodes , my lectuer asks me to decide a circuit a circuit to give the natural logarithm functionsz'" Vout = ln Vin"with these equiments , can anybody give me a hand? thanks a lots!!!!!!!!

 

[moamps]

Try "op amp logarithmic amplifier" in Google.

For example:
www.rmutl.ac.th/elecgmt2/lvw/wk8-Nonlinear%20Circuits_Log%20Amps.doc

 

[bcarso]

Try to use the "transdiode" circuit rather than a simple diode. The log conformance is much better. Keep your currents not much more than 100uA to reduce bulk resistance effects.

 

[CJ]

If you want to look cool in front of the teacher, look over a few of these patent docs at

http://www.audioannals.com/dbx.htm

and you can lay down more buzz words than Quaker has wifes. or whatever.

after you get an A+, the ol lady will want to get jiggy with you becuase she figures you have a future. :green: