Precision PCB Fabrication, PCB Assembly, Components sourcing, No MOQ...
We provide the most competitive PCB & PCBA products.
- All
- Product Name
- Product Keyword
- Product Model
- Product Summary
- Product Description
- Multi Field Search
Capacitors, resistors, inductors, connectors, and even the PCB are called passive because they don’t seem to consume power. But these apparently passive components can, and do, change the signal in unexpected ways because they all contain parasitic portions.
Transistors and ICs are considered active components because they change signals using energy from the power supply. Capacitors, resistors, inductors, connectors, and even the printed-circuit board (PCB) are called passive because they don’t seem to consume power. But these apparently passive components can, and do, change the signal in unexpected ways because they all contain parasitic portions. So, many supposedly passive components aren’t so passive.
Chip capacitors
Passive can be defined as inert and/or inactive. But passive electronic components can become an active part of a circuit in unexpected ways. Consequently, a capacitor that is purely capacitive simply does not exist. All capacitors inherently have parasitic components. The choice of the capacitor chemistry and construction can minimize some prarsitics.
Thinking more about signal frequencies and capacitors, we might forget about the harmonics or sideband that we create. For example, a real 50-MHz square-wave serial peripheral interface (SPI) clock will have odd harmonics to infinity. Most systems, but not all systems, can ignore harmonics above the fifth harmonic because the energy is so low that it is below the noise floor. However, the harmonics can still cause problems if they become rectified in a semiconductor and can be transformed into new lower-frequency interference.
The capacitors act as capacitors, but when they reach their lowest point and start upward, they become inductors(ESL) and are no longer effective as decoupling capacitors
What does this mean for our passive capacitors? We must understand that the tolerance we might expect, for example ±5%, may have a ±2% hole in the middle. We need to allow for this if the capacitor controls a critical frequency or timing. It also could mean that we need to plan on correcting wider variation with calibration.
