How does a phototransistor differ from a conventional BJT?

A phototransistor differs from a conventional bipolar junction transistor (BJT) primarily in its sensitivity to light. While a BJT relies on electrical current for operation, a phototransistor generates current when exposed to light, allowing it to function as a sensor. This makes phototransistors particularly useful in applications like light detection and optical communication. Additionally, phototransistors typically have lower gain compared to BJTs and are designed to be responsive to specific light wavelengths.