How is a diode an active device?

Active and passive components

In the field of electrical engineering, there are two types of components, passive and active components. Passive components are those components that have no amplifier effect and have no control function, while active components in some form show an amplifier effect of the useful signal or allow control.

What is a component in electrical engineering?

A component (in electrical engineering) is the smallest unit in a circuit (DIN 40150) that cannot be further dismantled, e.g. a resistor.

Difference between active and passive components

The above division into passive and active electronic components can also be easily remembered. Passive components behave passively, i.e. they have no amplifying effect on a signal, while active components can influence an applied signal in such a way that the signal can be amplified.

How can you determine whether the component is active or passive?

A rule of thumb can be used for this, which does not always apply (but almost always). As a rule, all electrical components (semiconductor components) that have at least one P-N transition are classified as active and all other components as passive.

Otherwise applies:
Passive components have constant and ideally independent electrical properties (e.g. capacitors (fixed capacitance value) and resistors (fixed conductivity value). A resistor with 100 ohms keeps the value 100 ohms (provided the temperature remains constant), even if the voltage applied to the Active components, on the other hand, change their electrical properties depending on physical effects, for example light in diodes.
The difference between active and passive components is particularly evident when comparing resistance and diode. The resistor has no “effective direction”, while the diode only lets the current through in one direction, so the diode is able to control an electrical signal.

Important: Electronic components, regardless of whether they are passive or active, are temperature-dependent in their current-voltage behavior.

Overview of passive and active components


passive components
active components
Oscillators and crystals
Processors / IC
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