What are Active Components?
Active components are electrical circuit elements that are capable of supplying electric power to a circuit or amplifying signals in the circuit. Active components are electric circuit elements that are capable of delivering power or power gain in an electric circuit.
They are able to supply electric power to the circuit or amplify the electric power in the circuit. Some common examples of active circuit elements are energy sources such as voltage sources or current sources, generators or alternators, and semiconductor devices such as transistors and photodiodes.
Active components play a critical role in the functioning of an electric circuit. They are responsible for controlling the flow of electric current in the circuit and they can also boost the power level of the electric signals. Active components receive energy from an external source and deliver it to the circuit in the form of electrical energy.
What is Voltage Source?
A voltage source is an electrical device with two terminals that generates a potential difference or voltage between them. The voltage produced by the source remains constant regardless of the amount of current drawn from the source. An ideal voltage source produces a constant voltage with zero internal resistance, making it 100% efficient.
However, in practice, having an ideal voltage source is impossible, and every voltage source has some internal resistance. This means that the voltage delivered by the source will not remain constant and will vary depending on the amount of current drawn from the source.
Examples of voltage sources include batteries, generators, alternators, and piezoelectric disks. They are commonly used in electronic circuits to provide a stable voltage for powering various electronic devices.
What is the Current Source?
A current source is a two-terminal device that produces a specified magnitude of current in the circuit regardless of the voltage across its terminals. An ideal current source provides a constant current output irrespective of the external circuit conditions or the load connected to it. An ideal current source has infinite internal resistance, which means it can deliver a constant current regardless of the load resistance.
In practice, it is difficult to achieve an ideal current source as all current sources have some internal resistance, which causes the current to vary slightly with changes in the external circuit conditions or the load resistance. Current sources can be classified as active or passive components depending on their ability to deliver power.
Examples of current sources include bipolar transistors, field-effect transistors, operational amplifiers, and photovoltaic cells. Current sources are used in a wide range of applications, such as biasing circuits, voltage regulators, battery chargers, and LED drivers, among others.
Transistor is Active Component:
A transistor is a three-terminal semiconductor device that can control current or voltage flow in a circuit. It consists of three layers of semiconductor material: the emitter, base, and collector. By controlling the current or voltage that is applied to the base terminal, the transistor can act as a switch or an amplifier.
When used as a switch, the transistor is either in an "on" state, allowing current to flow, or an "off" state, blocking the flow of current. In this way, transistors can be used in digital circuits to control the flow of binary information (0's and 1's).
When used as an amplifier, the transistor takes a small signal and amplifies it to a larger signal. This makes it useful in applications such as audio amplifiers, radio receivers, and other electronic circuits where amplification is needed.
Since a transistor can control current or voltage, it is considered an active element. It requires an external power source to function and can deliver power gain to the circuit.
Diode is an active component:
While diodes are commonly known as passive components, there are some types of diodes that exhibit negative differential resistance. In these types of diodes, the current flowing through the diode decreases with an increase in the applied voltage. This characteristic is opposite to that of a typical diode, which conducts current in only one direction.
Diodes with negative differential resistance, such as Tunnel diodes and Gunn diodes, have the unique property of being able to amplify electrical signals. This is because the negative differential resistance region of the diode can be used as an active element in a circuit, allowing the diode to control the flow of current and voltage.
Due to this capability, these types of diodes are considered active components, even though they are still technically diodes. They are used in various applications such as in microwave oscillators, detectors, and amplifiers, among others.
What are Passive Components?
Passive components are electrical circuit elements that do not require any external power source to function and are not capable of supplying electric power to a circuit or amplifying signals in the circuit. They can only absorb electrical energy and dissipate it in the form of heat or store it in either a magnetic field or an electric field. Passive components act as load in the circuit, and they help to control the flow of electric current and voltage in the circuit.
Passive components, on the other hand, can only absorb electrical energy and dissipate it in the form of heat or store it in either a magnetic field or electric field. Passive components cannot provide electric power or power amplification in an electric circuit. Some common examples of passive circuit components are resistors, inductors, capacitors, and transformers.
Passive components are important in an electric circuit because they can help control the flow of electric current and voltage. Resistors, for example, can limit the amount of current flowing through a circuit, while capacitors can store and release electrical energy.
The resistor is a passive component:
A resistor is a passive electronic component with two terminals that offers resistance to the flow of current passing through it. The resistance of a resistor is the measure of how much the resistor opposes the flow of current. A resistor is a passive component because it does not generate energy, rather it dissipates it in the form of heat.
Resistors are used in electronic circuits for a variety of purposes, such as:
- To limit the current flowing through a circuit, by offering a certain amount of resistance.
- To divide the voltage in a circuit, by forming a voltage divider circuit.
- To provide a load for an electronic circuit, by offering a certain amount of resistance.
- To filter high-frequency noise in a circuit, by acting as a low-pass or high-pass filter.
Resistors are available in different values of resistance, which are measured in ohms (Ω). The resistance of a resistor can be determined using Ohm's Law, which states that the resistance of a conductor is equal to the voltage across the conductor divided by the current passing through it.
Resistors are made of different materials, including carbon, metal film, and wire-wound resistors. The type of resistor used in a circuit depends on the application and the required precision.
Overall, resistors are one of the most basic and commonly used passive components in electronic circuits.
The inductor is a Passive Component:
An inductor is an electrical component of a coiled conductor, such as copper wire, wound around a magnetic core. When a current flows through the inductor, it generates a magnetic field around the coil, and this magnetic field stores energy in the form of electromagnetic radiation.
The amount of energy that an inductor can store is determined by its inductance, which is measured in henries. Inductors can be used in a variety of applications, such as filtering electrical signals, creating oscillators, and smoothing the output of power supplies.
Like other passive components, an inductor does not actively generate energy or amplify signals. Instead, it consumes energy and stores it temporarily in the form of a magnetic field. When the current flowing through the inductor stops or changes direction, the magnetic field collapses, and the stored energy is released back into the circuit.
Inductors are often used in combination with capacitors to create resonant circuits, which can selectively filter certain frequencies of an electrical signal while allowing others to pass through. They can also be used to smooth out a power supply's output, reducing voltage fluctuations that can damage electronic devices.
The capacitor is a Passive Component:
A capacitor is a two-terminal device that can store electrical energy in an electric field between its plates. When a voltage is applied across the terminals of the capacitor, one plate becomes positively charged and the other becomes negatively charged, and an electric field is established between them.
Capacitors are commonly used in electronic circuits for a variety of purposes such as smoothing out voltage fluctuations, filtering out noise, blocking DC signals, and storing energy.
Since a capacitor does not generate any electrical energy, it is considered a passive component. Instead, it only stores the electrical energy that is supplied to it by the circuit. When the capacitor is fully charged, it stops accepting any more energy and simply holds on to the energy it has already received.
When the capacitor is disconnected from the circuit, it can discharge its stored energy, releasing it back into the circuit. The rate at which a capacitor discharges its energy depends on its capacitance, the voltage it was charged to, and the resistance of the circuit it is connected to.
Therefore, a capacitor is an important passive component in electronic circuits, allowing them to perform a wide range of functions related to energy storage and signal processing.
Transformer is Passive Component:
A transformer is a two-coil device that consists of primary and secondary coils that are magnetically coupled. When an alternating current flows in the primary coil, it generates a changing magnetic field that induces a voltage in the secondary coil. This allows the transformer to step up or step down the voltage in an AC circuit.
A transformer does not generate any power or amplify signals, it simply transfers power from one circuit to another. Therefore, it is considered a passive component.
The power on the input side of the transformer is equal to the power on the output side, neglecting any losses due to resistance or magnetic hysteresis. This means that the transformer does not generate any power and only transfers power from one circuit to another.
Since the transformer operates on AC, it does not store energy like a capacitor or inductor. Instead, it transfers energy between the primary and secondary coils. Therefore, it is not an active component.
Overall, a transformer is a passive component that transfers power from one circuit to another by using mutual inductance.
Difference Between Active and Passive Component:
| Basis of Difference | Active Component | Passive Component |
|---|---|---|
| Definition | A component which can deliver power or power gain in an electric circuit for infinite duration of time. | A component which only absorbs power and converts it into heat or stores it in an electric or magnetic field. |
| Examples | Energy sources (voltage or current source), generators, semiconductor devices like transistors, solar cells, SCR, etc. | Resistors, inductors, capacitors, transformers, etc. |
| Role in the circuit | Behave as a source of power in the circuit. | Act as a load in the circuit. |
| Power gain | Can provide power gain in the electric circuit. | Cannot provide power gain. |
| Function | Receive energy in the forms of thermal, chemical, or hydraulic energy and deliver it in the circuit as electrical energy. | Receive electrical energy and either convert it into other forms such as heat, light, rotation, etc. or store it in a magnetic or electric field. |
| Control of current flow | Cause current flow in the circuit and control the flow of current. | Cannot control the current flow in the circuit. |
| Slope of VI graph | The slope of VI characteristics curve (i.e. the ratio of voltage to current) of an active element is negative. | The slope of VI characteristics curve (i.e. the ratio of voltage to current) of a passive component is positive at all points. |
| Quadrant of graph | The VI curve of an active element lies in the 2nd and 4th quadrant. | The VI curve of a passive element lies in the 1st and 3rd quadrant. |
| Power delivery or absorption | Can deliver as well as absorb electrical power. | Can only absorb electrical power. |
| Need of external power source to function | Some active components require an external power source to function. | Passive components do not require any external power source to function. |
| Amplification | Have power gain more than unity, so they can amplify a signal. | Power gain is less than unity, hence they cannot amplify a signal. |
Key differences between active and passive components:
- Definition: Active components are electrical components that can deliver power or power gain to an electric circuit for an infinite duration of time. Passive components, on the other hand, can only absorb power and convert it into heat or store it in an electric or magnetic field.
- Examples: Examples of active components include energy sources (such as voltage or current sources), generators, and semiconductor devices like transistors and diodes. Examples of passive components include resistors, capacitors, inductors, and transformers.
- Role in the Circuit: Active components behave as a source of power in the circuit, while passive components act as a load in the circuit.
- Power Gain: Active components can provide power gain in the electric circuit, while passive components cannot provide power gain.
- Function: Active components receive energy in the forms such as thermal energy, chemical energy, hydraulic energy, etc. and deliver it to the circuit in the form of electrical energy. Passive components receive electrical energy and either convert it into other forms such as heat, light, rotation, etc. or store it in the magnetic field or electric field.
- Control of Current Flow: Active components cause current flow in the circuit and control the flow of current. Passive components cannot control the current flow in the circuit.
- Slope of VI Graph: The slope of VI characteristics curve (i.e. the ratio of voltage to current) of an active element is negative, while the slope of VI characteristics curve of a passive component is positive at all points.
- Quadrant of Graph: For an active element, the VI curve lies in the 2nd and 4th quadrant, while the VI curve of the passive elements lies in the 1st and 3rd quadrant.
- Power Deliver or Absorb: Active components can deliver as well as absorb electrical power. Passive components can only absorb electrical power and are not capable of delivering power.
- Need of External Power Source to Function: Some active components require an external power source to function, while passive components do not require any external power source to function.