What are the main parameters of the transistor?

( 1 ) Collector's maximum dissipative power

PeM transistor will bear a large reverse voltage and heat through a larger current due to power consumption . When the power consumed by the collector junction ( the product of the collector current and the collector voltage ) is infinite, the high temperature will be generated and burn out. The maximum junction temperature of the PN junction is about 75 ℃~100 ℃, and the maximum junction temperature of the silicon tube is about 100 ~ 150  ℃. Therefore, the temperature of the collector of the transistor is not increased the power dissipated by the collector junction is the difference between the collector's maximum dissipation power PcN. The requirements of Pcm are also different. The limit value cannot be exceeded when using the transistor.

 ( 2 ) The common emitter current amplification factor

The common emitter current amplification factor is the base current Ib of the transistor, and the small change can cause the collector current Ie Big changes, that's the amplification of the transistor. Since both Ib and Ie. both use the emitter as the common electrode, the ratio of these two variations is called the common emitter current amplification factor.

When a small change is expressed, it refers to the difference between the quantity before the change and the amount of change. Commonly used small and medium power transistors, the value is about 20 to 250. The size of the value should be based on the requirements of the circuit to choose, not to excessive pursuit of a large number. Too large a tube, its linearity and work stability are often poor.

( 3 ) Breakthrough current Iceo refers to the current flowing through the collector when the base is open, and the specified reverse voltage is applied between the collector and the emitter. The penetration current is also an important criterion for measuring the quality of transistors. It is more sensitive to temperature and directly affects the temperature stability of the circuit.

At room temperature, the Iceo of the small power silicon tube is tens of microamps, the germanium tube is about a few hundred microamperes. Iceo's large tubes have poor thermal stability and short life.

(4) The maximum allowable current of the collector IcM is the maximum permissible current of the collector, which is called Leu when the collector current reaches to the allowable limit of the transistor. The collector current can not exceed Leu when using the tube, otherwise the transistor will become worse .

(5) The collector and base breakdown voltage BVCBO collector and base breakdown voltage refer to the reverse breakdown voltage of the collector when the emitter opens. In use, the reverse voltage between the collector and the base should not exceed BVCBO.

(6) The reverse breakdown voltage of emitter and base BVEBO emitter and base reverse breakdown voltage refers to the reverse breakdown voltage of the junction when the collector opens. Although a forward voltage is usually added to the transmission junction, when a large signal is transmitted, the emitter junction may withstand a reverse voltage at a negative half Zhou Feng value. The voltage should be far smaller than BVEBO, otherwise the transistor is easily damaged.

(7) The characteristic frequency f - tau characteristic frequency is the frequency corresponding to the current amplification factor (beta) falling to 1 in the common emitter circuit. If the transistor operates at a higher frequency than the characteristic frequency, the transistor will lose its current amplification capability.

(8) Collector reverse current IcBo refers to the reverse current of the collector junction when the emitter opens. It does not increase with the increase of the reverse voltage, so it is also called reverse saturation current. At room temperature, the IcBo of the low power germanium tube is about 10, and the IcBo of the small power silicon tube is less than 1. The size of IcBo  marks the quality of the junction, and a good transistor IcBo  should be very small.

(9) The collector and emitter reverse breakdown voltage BVcEO collector and emitter reverse breakdown voltage refer to the maximum working voltage between the collector and the emitter when the base is open. If the collector voltage is too high, the transistor will break down, so the voltage applied to the collector should not be higher than BVcE0. Generally, the BVcEo should be twice as high as the power supply voltage.

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