A Light Dependent Resistor (LDR) is a type of resistor that changes its resistance in response to the amount of light that falls on it. It is also known as a photoresistor or photocell. The resistance of an LDR decreases as the light intensity increases.
A Phototransistor is a type of transistor that is activated by light. It is a light-sensitive device that is used to detect light and convert it into an electrical signal. When light falls on a phototransistor, it causes a change in the amount of current flowing through it.
The main difference between an LDR and a phototransistor is that an LDR is a passive component, meaning it does not require an external power source to function. On the other hand, a phototransistor is an active component and requires a power source to operate.
LDRs are commonly used in light sensors, camera exposure control, and automatic street light systems. Phototransistors are used in applications such as light meters, burglar alarms, and optocouplers for electrical isolation.
It depends on the application and the specific components. Generally, phototransistors tend to be more sensitive than LDRs. However, LDRs have a wider range of resistance and can be used in a broader range of light intensities.