The parameters of triode can be divided into DC parameters, AC parameters, limit parameters and characteristic frequency. The parameters of triode are an important basis for the use and selection of triode. Therefore, understanding the parameters of triode can avoid the damage of tube caused by improper selection or use. Today, our article introduces the four parameters of Lujing triode, which is commonly used in the market.





1. DC parameters





Collector base reverse current I (CBO). When the emitter is open and a specified reverse voltage is applied between the collector and the base, the leakage current in the collector junction is called I (CBO). The smaller this value is, the better the thermal stability of the transistor is. Generally, the small power tube is about 1o μ About a, the silicon tube is smaller. Collector Emitter reverse current I (CBO) is also called penetrating current. It refers to the leakage current of the collector when a specified reverse voltage is added between the collector and the emitter when the base is open circuit. The smaller the value, the better. The silicon tube is generally small, about 1 μ Below a. If this value is found to be large in the test, the tube is not easy to use.





2. Limit parameters





Maximum allowable collector current I (CM) when the triode β When the value drops to half of the maximum value, the collector current of the tube is called the maximum allowable collector current. When the collector current IC of the tube exceeds a certain value, it will cause changes in some parameters of the transistor, the most obvious is β The value decreases. Therefore, in practical application, IC should be less than I (cm °) and the maximum allowable dissipation power P (CM) of the collector. When the transistor works, the collector junction will heat due to the dissipation of certain power by the collector. When the temperature is too high, it will lead to the change of parameters and even burn the transistor. Therefore, it is stipulated that the maximum dissipated power of the collector will be the power consumed when the temperature of the transistor collector rises to such a level that it will not burn the collector. In order to improve the P (CM) value during use, heat sink can be added to the high-power pipe. The larger the heat sink, the more the P (CM) value will be improved. Collector Emitter reverse breakdown voltage bu (CEO) the maximum voltage allowed between collector and emitter when the base is open circuit. In practical application, the voltage added between collector and emitter must be less than bu (CEO), otherwise the triode will be damaged.





3. Current amplification factor





DC amplification factor β "Or expressed by H (FE). It refers to the ratio of the common emitter circuit, collector output DC I (b) and base input DC when there is no AC signal. That is: β= I(c)/I(B) β It is an important parameter to measure the current amplification ability of triode, but for the same triode, there are different characteristics under different collector currents β. AC amplification factor β It can also be expressed by H (FE); this parameter refers to the ratio of the change of collector current △ AIC to the change of base current △ I (b) in the common emitter circuit when there is AC signal input, i.e β= △ IC / △ I (b) the above two parameters show the amplification ability of the triode to DC current and AC current respectively, but because the values of these two parameters are approximately equal, that is β ≈ β， Therefore, it is generally no longer distinguished in actual use. Due to the production process, even if the pipes produced in the same batch are different β The value is also different. For convenience and practicality, manufacturers sometimes mark the body value on the triode for users to choose.





4. Characteristic frequency





Because the corpse value decreases with the increase of working frequency, the higher the frequency, β The more serious the drop is. The characteristic frequency of the triode refers to the frequency value when the corpse value drops to 1. That is, the triode working at this frequency has lost its amplification ability, that is, f (T) is the limit frequency in the use of the triode. Therefore, when selecting the triode, the characteristic frequency of the tube is at least 3 times higher than the 1 operating frequency of the circuit. But not f (T) The higher the better. If you choose too high, it will cause the oscillation of the circuit.