The C1815, also commonly marked as 2SC1815, is a small signal NPN bipolar junction transistor made in Japan originally by Toshiba. It is not a power transistor like the 13001 but rather a general-purpose device used in low-current, low-noise amplification and switching. Because it is cheap, reliable, and widely available, it has been used for decades in audio circuits, radios, and consumer electronics.
A simple example circuit is using C1815 to amplify a microphone signal. The following shows a simple small signal amplifier build with 2SC1815 tansistor.
Its typical ratings are a maximum collector-emitter voltage of around 50 volts, a collector current up to about 150 milliamps, and a power dissipation of around 400 milliwatts in a TO-92 plastic package. The current gain (hFE) is fairly high, usually between 70 and 700 depending on the grade and operating conditions, which makes it good for signal amplification. It also has low noise characteristics, which is why it is often found in audio preamplifiers or radio frequency input stages.
In practical use, the C1815 might be placed in the input stage of an audio amplifier to amplify weak signals from a microphone or other sensor before passing them to stronger stages. It is also used as a general-purpose switching transistor in logic circuits, LED drivers, or small relay drivers when the required current is modest.
In summary, the C1815 is a versatile small signal NPN transistor designed for low noise amplification and light switching, suitable for audio and general low-power electronic applications.
