Active Capacitance Explanation:
Active capacitance refers to the capacitance that is deliberately added to a circuit for specific purposes. It is an essential component in the design of many electronic circuits and devices.

Diffusion Capacitance:
- The active capacitance is also known as diffusion capacitance in semiconductor devices.
- This type of capacitance is associated with the charge storage in the depletion region of a PN junction.

Role in Semiconductor Devices:
- In semiconductor devices such as diodes and transistors, diffusion capacitance plays a crucial role in determining the device's speed and performance.
- It affects the switching speed and charging/discharging characteristics of the device.

Effect on Performance:
- Diffusion capacitance can impact the overall performance of semiconductor devices by influencing their frequency response and signal propagation.
- It is important to consider and optimize diffusion capacitance in the design of high-speed circuits.

Comparison with Other Capacitances:
- Diffusion capacitance is different from parasitic capacitance, which refers to unintended capacitance present in a circuit.
- While diffusion capacitance is an intentional component designed for specific purposes, parasitic capacitance can have adverse effects on circuit performance.
In conclusion, active capacitance, also known as diffusion capacitance, plays a significant role in the operation and performance of semiconductor devices. It is a deliberate component added to circuits to control charge storage and improve device characteristics. Understanding and optimizing diffusion capacitance is essential for designing efficient and high-speed electronic circuits.