**Basic Antilog Amplifier Using Diode:**

The circuit diagram of basic antilog amplifier using diode is shown in the Fig. 2.70.

The positions of diode and resistance are exchanged as compared to log amplifier circuit. The node A is grounded and hence node B is at virtual ground. Hence V_{B} = 0.

Now the current flowing through the diode is I_{f} and the voltage across diode is V_{in }itself, as B is at virtual ground. Hence from the diode current equations we can write,

As op-amp input current is zero, the current I must be same as I_{f}.

The product I_{o }R_{f} can be assumed to be V_{ref}, so we get,

Thus the output voltage is proportional to the exponential function of V_{in}. The exponential function is nothing but the antilog and thus circuit works as an antilog amplifiers.