The film capacitor has many excellent characteristics, so it is a capacitor with excellent performance. The characteristics of  film capacitors are mainly as follows: non-polarity, high insulation resistance, excellent frequency characteristics (wide frequency response), and small dielectric loss. Based on the above advantages, film capacitors are widely used in analog circuits. Especially in the part where the signal is connected, a capacitor with good frequency characteristics and extremely low dielectric loss must be used to ensure that the signal is transmitted without too much distortion.
Its structure is the same as paper dielectric capacitor, and the medium is polyester or polystyrene. Polyester film capacitors have high dielectric constant, small size, large capacity, and good stability. They are suitable for bypass capacitors. Polystyrene film capacitors have low dielectric loss and high insulation resistance, but have large temperature coefficients and can be used in high-frequency circuits.
Among all plastic film capacitors, polypropylene (PP) capacitors and polystyrene (PS) capacitors have the most significant characteristics. Of course, the prices of these two capacitors are relatively high. However, in recent years, in order to improve the sound quality of audio equipment, the parts materials used have become more and more advanced, and the price is not the most important consideration. Therefore, the frequency and number of PP capacitors and PS capacitors used in audio equipment have also increased The higher. Readers can often see equipment of XYZ brand, claiming how many PP-type capacitors or PS-quality capacitors of XYZ brand are used as an endorsement in sound quality, the reason is here.
Summary of the characteristics of  film capacitors: The capacity range of thin film capacitors is 3pF-0.1μF, the DC operating voltage is 63-500V, suitable for high frequency and low frequency, and the leakage resistance is greater than 10000 Ω.

Characteristics of film capacitors