Function of three-terminal capacitor

Capacitors are indispensable components in circuits, especially filter capacitors, which are used everywhere. Generally, the capacitance has two electrodes. However, there is a type of capacitor with three terminals called a three-terminal capacitor. It has better characteristics than general two-terminal capacitors at high frequencies. Then let's take a look at this three-terminal capacitor, take a look at its structure, performance, and installation method.

For chip capacitors, three-terminal capacitors are actually four-terminal. Everyone knows that capacitors have ESL and ESR, that is, parasitic inductance and parasitic resistance. The high frequency characteristic of the capacitor is an inverted V type.

At the beginning, it has a capacitive characteristic, the higher the frequency, the smaller the impedance. When the resonant frequency point of the capacitor is reached, the higher the frequency, the parasitic inductance will play a leading role. Then it presents inductive characteristics, the higher the frequency, the greater the impedance. The latter part is what we don't want, we hope that the higher the frequency, the lower the impedance.

The three-terminal capacitor is to reduce this parasitic inductance, so this resonant frequency can go a little higher. For a chip three-terminal capacitor, actually it has four terminals, it divides the two-terminal capacitor into four terminals.

It divides the parasitic inductance of a capacitor into four parasitic inductances, and the two inductances are connected in parallel, and the parasitic inductance is reduced by half. In this way, its capacitance has not changed, and its parasitic inductance has been reduced by half, which greatly improves the characteristics of high-frequency capacitors and makes the performance of the capacitor better.

How is it installed? As shown in Figure 3 above, the red power or signal line in the middle is disconnected, connect the through two ends of the three-terminal capacitor, and the other two ends of capacitor are connected to the ground.

However, three-terminal capacitors are a bit more expensive than ordinary capacitors. This should be a consideration of cost and performance!