MPSA18 (NPN Low Noise Transistor)

The MPSA18 is a NPN General Purpose Transistor with a low noise high gain property. Meaning it can amplify even a very low power signal with a good signal to noise ratio. As we know an amplifier amplifies both the signal and noise of the input signal, a low noise transistor like MPS18 can be used to build Low Noise Amplifiers (LNA) which can avoid the noise being amplified and thus providing a good signal to noise ratio even at high gain. Hence the MPS18 can be found in most low power audio amplifier circuits.

Apart from this, the transistor also can be used for general purpose switching applications.  It can switch loads upto 45V with a load current of 200mA. The base can be triggered with 7V to control the switching of the transistor.