Hello Everyone,

I’m looking for some help with calculating the dynamic range of the logarithmic op-Amp circuit below. Can someone please direct me?

You can assume any values. Opamp dynamic range define as follows:

DR = 20 Log (Vout(max)/Vout(min))

 

In the following MT-077 TUTORIAL
http://www.analog.com/static/imported-files/tutorials/MT-077.pdf in Page number 4 mentioned
"the dynamic range of this configuration (The Diode / Op-Amp Log Amp) is limited to 40-60 dB because of non-ideal diode characteristic, but if the diode is replaced with a diode-connected transistor as shown in Figure 7, the dynamic range can be extended to 120 dB or more"

Can anyone explain this please? and I would like to calculate the dynamic range for both circuit!!