ok
i red 2sc2681 datasheet but would you plz give alittle explanation :
I can't find this in the datasheets I checked
I think you are refering to Vcbo (maximum voltage collector to base) and Vceo (maximum voltage collector to emitter)
This is maximum current and power for the device, but it is only good if you can keep the case temperature at 25C
80 MHZ? Transistion frequency from wiki:
For transistors, the current-gain–bandwidth product is known as the fT or transition frequency.[3][4] It is calculated from the low-frequency (a few kilohertz) current gain under specified test conditions, and the cutoff frequency at which the current gain drops by 3 decibels (70% amplitude); the product of these two values can be thought of as the frequency at which the current gain would drop to 1, and the transistor current gain between the cutoff and transition frequency can be estimated by dividing fT by the frequency. Usually, transistors must be applied at frequencies well below fT to be useful as amplifiers and oscillators. [5] In a bipolar junction transistor, frequency response declines owing to the internal capacitance of the junctions. The transition frequency varies with collector current, reaching a maximum for some value and declining for greater or lesser collector current.