Op amp circuit for logrithm calculation?
For a BJT, \$V_{BE} \approx\$ \$V_T \cdot ln(\$ \$ I_c \over I_S\$), where \$V_T = \$\$k \cdot T\over q\$, and \$I_S \$ is a transistor characteristic (saturation current). 

So, it's a matter of scaling to get what you're asking for. 

Recall that \$log_{10}(x)\$ = \$  ln(x)\over ln(10) \$. 



The devil is in the details, however, and both \$I_S\$ and \$ V_T\$ are temperature dependent, so compensation is required, perhaps with a temperature-dependent resistance. 

See this answer.