R-Capacitance Sensitivity

I would like to simulate a simple R-C circuit where capacitance is changed and its change is very small such as cca. 0.5pF and its baseline is 50pF and circoiut resistance is 200Ohm. I use a voltage-controlled current source to enforce a constant alternating current 0.01 peak amplitide, with 100kHz freqquency.

I would like to see the voltage change due to capacitance change - unfortunately, I can't see it - how can I set the Simulink environment to see it change there?

Answer 1

[Pratyush]

Hi Peter,

To simulate the R-C circuit in Simulink and observe the voltage change due to a small change in capacitance, you will need to configure the Simulation Parameters. In "Model Configuration Parameters" :

• set the "Stop Time" to a value that allows you to observe several periods of the sine wave, such as 0.001 seconds (1ms),
• set the "Solver" to a suitable type, like "ode45 (Dormand-Prince)" for a more accurate result.
• set the "Max step size" to a small value to capture the small changes, such as 1e-7 seconds.

To see the small change in voltage due to the 0.5 pF change in capacitance, you may need to zoom in on the Scope plot or adjust the Scope settings to increase the Y-axis resolution. Simulink's visualization tools might not be sensitive enough to clearly show such a small change in the voltage directly. If you cannot see the change, you can log the data to the MATLAB workspace and use MATLAB's plotting functions to get a more detailed view of the voltage changes.