The voltage across the capacitor cannot be abruptly changed. To understand this, you must understand what kind of properties the capacitor is. Yes, it is an energy storage component. Capacitor, as the name suggests, is a container for electrical energy, like a water cup, which is a container for holding water. So is the water cup better than the water capacity?
The voltage across the capacitor cannot change suddenly, just like pouring water into an empty cup, you can't fill the cup with water instantly, and electricity can't charge the capacitor instantly. It takes time to fill the cup with water and fully charge the capacitor. Although this time (τ=RC) may be very short, it is a process after all, and it cannot be completed in an instant.
Combined with the above description, let's use Tina to simulate the integral circuit and the differential circuit.
2.1.1 Integral simulation circuit
2.1.2 Integrating circuit simulation waveform
In the above figure, the green square wave signal is the original input signal, that is, the signal source signal. Brown is the output signal, that is, the signal waveform at both ends of the capacitor.
It can be seen that when the input signal changes from low level to high level, this change process is completed almost immediately, but this change process is reflected on the capacitor is very different, the voltage change on the capacitor is relatively slow, it is a process of charging and discharging, the voltage increases from 0, and the entire high level period of the input signal is the charging time. Due to the selection of τ=RC parameter, the charging of the capacitor has not reached the amplitude of the input signal, and the input signal becomes 0. At this time, it starts to discharge again, and it starts to charge again before the discharge is finished. It just keeps looping. The above waveform appears. Differential circuits can also be analyzed in the same way.