Passive and Active networks and systems refer to how different components within a circuit behave in terms of energy:
1. Passive Networks/Systems:
- A passive network consists of components that do not generate or amplify electrical energy; they can only consume, store, or dissipate energy.
- Passive components cannot provide gain or energy; they rely solely on the energy supplied by external sources.
- Examples of passive components:
- Resistors: Dissipate energy as heat.
- Capacitors: Store energy in the form of an electric field.
- Inductors: Store energy in the form of a magnetic field.
- Characteristics:
- They do not require an external power source to operate (though they may need an external power supply to interact with).
- Energy loss may occur in resistors (heat) or energy storage in inductors/capacitors.
Applications: Passive networks are often used in filter circuits, impedance matching, and in systems where signal conditioning without amplification is required.
Key Points:
- No amplification of signal.
- Only consume or store energy.
- Use of Ohm’s law, Kirchhoff’s laws for analysis.
2. Active Networks/Systems:
- An active network contains components that are capable of generating or amplifying electrical signals. Active components can control the flow of current and can introduce energy into the system, typically from an external power source.
- Active components are used for amplification, oscillation, and switching in circuits.
- Examples of active components:
- Transistors: Can amplify signals.
- Operational amplifiers (Op-Amps): Provide voltage amplification and can perform various functions like filtering, summing, and integration.
- Diodes: Control the direction of current flow and can also be used in active devices like rectifiers and voltage regulators.
Characteristics:
- They require an external power source to function.
- Can amplify signals or control voltages and currents.
- Used in applications such as signal amplification, oscillators, and active filters.
Applications: Active networks are used in amplifiers, signal processing, and any system requiring control or manipulation of electrical energy beyond what is provided by the input signal alone.
Key Points:
- Can amplify or generate electrical signals.
- Requires external energy source (e.g., batteries, power supplies).
- Common in signal amplification, modulation, and switching circuits.
Comparison between Passive and Active Networks:
| Passive Networks | Active Networks |
| Consist of passive components (resistors, capacitors, inductors). | Contain active components (transistors, op-amps, diodes). |
| Cannot generate or amplify electrical signals. | Can generate or amplify signals. |
| Only consume, store, or dissipate energy. | Can introduce additional energy into the system. |
| Analysis typically uses Kirchhoff’s and Ohm’s laws. | Analysis involves complex concepts like feedback and gain. |
| Do not need an external power source. | Require external power to function (e.g., batteries or power supplies). |
| Example: Low-pass filter with only resistors and capacitors. | Example: Amplifier circuit with transistors or op-amps. |
Example:
- A passive low-pass filter made of just a resistor and a capacitor filters out high frequencies without any amplification.
- An active low-pass filter that includes an operational amplifier can both filter and amplify the signal.