According to Wikipedia, the following is the exponential output operational amplifier.
I would like to test this out in a simulated environment and see how this functions. For example give a sine wave as the input and observe the resulting output signal.
But I do not have any prior knowledge about simulating electrical circuits. Could somebody help me out here by suggesting a way to get started with this ? Thanks!
Best Answer
The circuit topology you are showing is an exponential amplifier (an antilog), where the output voltage is proportional to the exponent of the input voltage.
How to simulate it? and in Simulink (as per the tags), by building a model. That is where the annoyance comes from. An antilog amplifier works because of the exponential characteristics of a PN junction and thus to simulate this you must model this characteristic.
This is where the specifics of the simulation packages becomes important. The modeling of the diode can be split into 3
For simulink, the base Simscape's electrical domain only offers #2. The Electronics module does offer an exponential model and this is key as this is the behaviour such an amplifier relies on.
The current equation of a diode can be summaries as \$ I_f = I_{o} \cdot e^{ \frac{V_{in}}{V_t}} \$
Assuming ideal opamp and thus If must be the current flowing through the feedback resistor
\$I = I_f = \frac{V_- - V_o}{R_f} = \frac{-V_o}{R_f} \$
\$V_o = -I_o R_{fb} e^{ \frac{V_{in}}{V_t}} \$
If you really want to model such a circuit, look into SPICE-based simulators as you need the characteristics of the diode.