The 2SC1345 is a low signal NPN amplifier transistor with a collector to emitter voltage of 50V and collector current of 100mA. The Transistor has a high gain value from 250 to 1200 making it suitable for amplifier designs.
The 2SC1061 is a NPN Power Transistor in To-220 package. It has a DC current gain from 35 to 320 and transition frequency of 5MHz. It is commonly used in high power amplifier application along with its complementary PNP part 2SA671.
The BC546 is a high frequency NPN Transistor commonly used in low noise amplifier designs. It has a maximum gain value of 800 and a high collector to emitter voltage of 65V making it also suitable for high voltage audio amplifier applications.
The MPF102 JFET is a popular N-Channel JFET that is commonly used in low power amplifier circuits. The JFET is no longer in production and finding it might be difficult. So they are not recommended for new designs.
The MPSA18 is a General Purpose NPN Transistor which can operate with low noise and high gain. The transistor has a gain value of 500 to 1500 and can operate at a voltage of 45V with 200mA load current.
The KST42 is a SMD package NPN Transistor that has high collector emitter voltage of 300V and a collector current of 500mA. The transistor is a general purpose transistor and can be used for both switching and amplification purpose.