Types of passive devices, the difference between active and passive devices

Passive components mainly include resistors, capacitors, inductors, converters, gradients, matching networks, resonators, filters, mixers and switches, etc. An electronic component that can display its characteristics without the need for an external power supply. Passive components are mainly resistive, inductive and capacitive devices, and their common feature is that they can work when there is a signal in the circuit without adding a power supply.

When an electric current passes through a conductor, the property of the internal resistance of the conductor that hinders the current is known as resistance. The components that play a role in blocking the flow in the circuit are called resistors, or resistors for short. The main use of resistors is to step down, divide or shunt, and are used as loads, feedback, coupling, isolation, etc. in some special circuits.

The symbol of the resistor in the circuit diagram is the letter r. The standard unit of resistance is ohms, denoted as . Also commonly used are kiloohm k and megaohm m.

IK = 1000 1M = 1000K Capacitors are also one of the most common components in electronic circuits, it is a component that stores electrical energy. A capacitor consists of two identical conductors sandwiched between a layer of insulating dielectric. When a voltage is applied to its ends, a charge is stored on the capacitor.

Once there is no voltage, it will release electricity again as long as there is a closed loop. Capacitors block DC passage in the circuit while allowing AC to pass, and the higher the frequency of AC, the greater the ability to pass. Therefore, capacitors are commonly used in circuits for coupling, bypass filtering, feedback, timing and oscillation.

Capacitors have the letter code C. The unit of capacitance is farad (denoted as f), which is commonly used in f (micro-method) and pf (i.e., f, pico-method).

1f=1000000μf=10^6μf=10^12pf 1μf=1000000pf

The behavior of capacitors in a circuit is nonlinear. The impedance to the current is called capacitive reactance. Capacitive reactance is inversely proportional to the capacitance and frequency of the signal.

An inductor, like a capacitor, is also an energy storage component. Inductors are generally made of coils, and when AC voltage is added to both ends of the coil, an induced electromotive force is generated in the coil, which hinders the change of current through the coil. This obstacle is called inductive resistance.

The inductive reactance is proportional to the amount of inductance and the frequency of the signal. It does not hinder direct current (not counting the DC resistance of the coil). So the role of inductance in electronic circuits is:

Current resistance, voltage transformation, coupling and with capacitors are used for tuning, filtering, frequency selection, frequency division, etc.

The inductor is coded L in the circuit. The unit of inductance is henry (denoted h), and the commonly used are millihen (mh) and micro hen (h).

1h=1000mh 1mh=1000μh

Inductors are typical components for electromagnetic induction and electromagnetic conversion, and the most common application is transformers.

Difference 1: Whether an external power supply is required.

A passive device is a device that can independently exhibit its external characteristics without relying on the presence of an external power supply (DC or AC). Beyond that are the active devices. The term "external characteristic" describes a certain relationship of a device, albeit in terms of voltage or current, electric or magnetic field, pressure, velocity, and so on.

Difference 2: Whether or not power is provided.

In order for an active device to work normally, in addition to the electrical energy in its own functional circuit, it is also necessary to provide it with a normal working power supply, such as transistors, field effect transistors, and most integrated circuits full of transistors. When the passive device works normally, it does not need to provide additional power supply, and the difference is three: the difference in harmonic generation.

Passive components do not generate harmonics when operating, only noise and phase shifts, and are used by passives for signal transmission or "signal amplification" through directionality. Active devices are generally used for signal amplification, conversion, etc., and active devices will produce various harmonics when working, which distorts the output.

Difference 4: The nature of the circuit is different.

From the perspective of circuit properties, active devices and passive devices have two basic characteristics. The active device itself either consumes electrical energy, or converts electrical energy into other forms of energy, and only needs to input a signal and does not need an external power supply to work normally. It also consumes electrical energy, and in addition to the input signal, it must also have an external power supply to work normally.

The components of the active circuit include energy storage components such as motors, coils, and capacitors; The components of a passive circuit include components other than energy storage components such as motors, coils, and capacitors.

The so-called active circuit and passive circuit are divided according to whether the power supply is included in the electric digging key annihilation circuit, and the active circuit is the circuit that contains the power supply; A passive circuit is like an impulse circuit that does not contain a power supply.

After the power supply is disconnected, motors, coils, capacitors, etc., have a certain electromotive force, which can provide electrical energy to other circuit components.