Log Amplifier
The inputs are ac-coupled by C1, C2, and terminated with a 52.3 W resistor that combines with the AD8306’s input resistance of 1000 W to give a broadband input impedance of 50 W. The R-C combination produces a high-pass corner frequency of around 600 kHz (1/(2πRC)), where C = (C1)/2. In high frequency applications,this corner frequency should be placed as high as possible, to minimize the coupling of unwanted low frequency signals. In low frequency applications, a simple RC network forming a lowpass filter should be added at the input for the same reason. If the limiter output is not required, Pin 9 (LMDR) should be left open and Pins 12 and 13 (LMHI, LMLO) should be tied to VPS2 as shown in the figure below.
