Passive Electronic Components: Building Blocks of Electronic Circuits

June 10, 2019 Cadence PCB Solutions

Group of active people earth plastering a home

 

 

Everyone knows the difference between an "active" person and a "passive" person. The active person has a busy life and takes action, whereas the passive person is usually kind of bland, compliant, lets life happen to them. In the world of electronics, however, passive electronic components are powerful gatekeepers -- loudmouth signals that threaten the integrity of the circuit are gobbled up and held captive, or spit out as heat. Passive electronic components are fierce defenders against signals that are too high.

Passive electronic components are hot news in the electronics world, as these critical devices are required in increasingly larger numbers for mobile phones, the Industrial Internet of Things (IIoT), voice-controlled smart speakers, the smart watch, smart appliances, artificial intelligence (AI), and the electric car.

It is the capability of electronic components to act as switches that makes the process of transmitting digital information possible. By controlling and manipulating the flow of electrons through specially designed networks of electronic components, we are able to create a circuit that delivers a specific outcome. Passive electronic components are required to protect circuits from receiving signal levels that are too high for the desired function. For example, a passive electronic component such as a resistor may be used to dissipate an amplifier's excess power in order to reduce the volume of sound produced by the speaker.

It is the interconnection between passive and active electronic components that define the function of the circuit. So, what makes a component "active" or "passive", and which components are used to achieve these individual states?

Passive Electronic Components: Functions and Uses

Passive components store energy or dissipate it. They do not require electrical power to operate outside of the alternating current (AC) circuit that it is connected to. Being "passive" means these devices cannot generate or increase a signal, amplify its frequency, or add direction to the circuit flow.

Passive electronic devices are bi-directional -- they can be connected either way within a circuit unless they have a specific polarity indicator. The polarity of the voltage across them is determined by current flow from the positive to the negative terminal.

Examples of passive devices that can store or deliver energy but cannot generate it, are two-terminal components such as resistors, inductors, capacitors and transformers. Being passive, these devices are able to attenuate or reduce the power of a signal without appreciably distorting its waveform.

Two types of passive electronic components:

  1. Lossy or Dissipative: Tendency to lose or dissipate the incoming power flow. An example would be a resistor, a passive electronic component that opposes the flow of electrical current through it, then dissipates the energy as heat.

  2. Lossless: Passive electronic components that can store energy indefinitely with no energy lost as heat. For example, capacitors and inductors are similar electronic components that impede the current, but they store the energy instead of dissipating it. A capacitor stores energy in an electric field as a charge across its plates, while an inductor stores energy in a magnetic field within the turns of a coil.

Active vs. Passive Electronic Components: Differences and Uses

Electronic engineers apply the terms passive and active in conjunction with circuit analysis — discovering the currents through, and the voltages across, every component in the network.

 

ACTIVE

PASSIVE

Power Source

External to circuit

Circuit

Supplies Power to Circuit

Yes

No

Amplifies a Signal

Yes

No

Stores Energy

No

Yes

Produces a Power Gain

Yes

No

Control current flow

Yes

No

Examples

Transistor, oscillator, amplifier, integrated circuits, LEDs, diodes

Resistors, inductors, capacitors and transformers

 

Outlook for Passive Electronic Components in 2019

Since 2017 there’s been a component shortage in a range of passive electronic components including resistors, diodes, and especially ceramic capacitors, with lead times increasing each year. In 2017-18, most companies went below their comfort threshold in multi-layer ceramic chip capacitor (MLCC) inventory. The shortages for these higher capacity MLCCs are now anticipated to reach to 2025.

The multi-layer ceramic chip capacitor is the workhorse of the electronic components industry. MLCCs are unique in that they far exceed other dielectrics capabilities in creating capacitance in a very small case size. These passive electronic components are relied upon and used across multiple industries such as mobile phones, smart watches and portable computing, electric vehicles, TV sets, home automation, home appliances and home smart speakers (e.g. Amazon Echo Dot), and video cards for crypto-currency trading. These consumer-driven, power hungry electronic applications will pay large premiums for components due to the shortage of multi-layer ceramic chip capacitors.

 

Group of electronic components splayed on a schematic

Passive electronic components may present difficulty due to supplier constraints

 

There are no immediate global solutions to the shortage of these particular passive electronic components. Original equipment manufacturers (OEMs) and electronics manufacturing service (EMS) providers are scrambling to create alternative designs to limit their exposure to the high capacity ceramic chips.

Crises such as this passive electronic MLCC shortage we are experiencing create a climate of mutual need for EMS providers and OEMs alike. This crisis provides an opportunity for OEMs and EMS providers to forge closer relationships by tapping on the strengths, knowledge base, and supplier contacts each bring to the table.

There are proactive steps that original equipment manufacturers (OEMs) and electronics manufacturing service (EMS) providers may take to limit their risk factor during this shortage crisis for MLCCs.

Steps for OEMs:

1) Refine forecast accuracy for EMS providers by giving them the most accurate and current forecast of your production demands and materials so they can stage their operations with confidence.

2) Use your supply chain influence to contact divisions of large companies that already have existing stock, allocation contracts, or the ability to turn quick deliveries. Letters of authorization may enable immediate action. You may need to place larger orders or offer residual stock buyout guarantees.

3) Pursue design alternatives minimizing future MLCC exposure, evaluating rating differentials such as tolerance, construction, or voltage. Avoid reliance on obsolescence or legacy products. Shift package sizes downward and redesign current layouts.

Steps for EMS Providers:

1) Exert buying power leverage wherever possible, including letter of authorization (LOA) requests.

2) Risk buy, but with limited liability for both partners. Lengthen distributor accounts payable terms.

3) Keep the level of supply chain communication high and responsive. Be prepared to react at whatever stage of change is needed by the OEM.

Technology partners should be an integral part of an electronics company's manufacturing team. For electronics designers and manufacturers, Cadence provides unparalleled expertise, software tools, and hardware required for the entire electronics design chain, from chip design to chip packaging to PCBs and complex systems.

If you’re looking for a suite of customizable tools capable of resolving any design issue, consider Cadence’s suite of layout and analysis tools. OrCAD’s PCB Editor can assist with redesigns to limit future exposure to an ongoing MLCC shortage.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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