The main parameters of the first,triode
The main parameters of the first,triode
Current amplification factor beta
The current amplification factor is the current magnification,which is used to indicate the amplifying power of the transistor.According to the working state of the triode,the current amplification coefficient is divided into DC amplification factor and AC amplification factor.
The DC magnification coefficient refers to the ratio of the collector current Ic to the base current Ip when the static signal is not transmitted,so it is also called the DC magnification or static amplification factor,which is usually expressed in hFE or beta.
The amplification coefficient of the AC current is also called the dynamic current amplification factor or the AC magnification, which refers to the ratio of the change of the collector current to the base current in the alternating state,and is usually expressed in beta.Beta is an important index to reflect the magnification of the triode.
Dissipative power PcM
Dissipative power,also known as collector maximum allowable dissipative power Pom,refers to the maximum collector dissipative power when the triode parameters do not change beyond the prescribed allowable value.
frequency characteristic
The current amplification factor of the triode is related to the working frequency. If the triode exceeds the working frequency range,the magnifying capacity will be reduced and even the amplification will be lost.
Collector maximum current IcM
The maximum current of the collector is the maximum current allowed by the collector of the triode.When the collector current Ic rises,the triode's beta decreases.When the beta falls to 2/3 of the normal value,the collector current is IcM.
Maximum reverse voltage
The maximum reverse voltage refers to the maximum working voltage allowed by the transistor when it is working.The maximum reverse voltage includes the reverse breakdown voltage of the collector emitter UcBo,the collector base reverse breakdown voltage UcBO, and the emitter base reverse breakdown voltage UEBO.
Reverse current
The reverse current of the transistor includes the reverse current IcEo between the collector current base IcBO and the collector emitter.
The selection of two and triode
The selection of general small power triode
When the triode is selected,it is necessary to make clear that the frequency of the electronic circuit is about how much.In the engineering design,the characteristic frequency of the triode is
times that of the actual working frequency.Therefore,the characteristic frequency of triode can be chosen according to this requirement.
The selection of the small power triode BVCEO can be determined according to the power supply voltage of the circuit.In general,as long as the BVCEO of the triode is larger than the maximum voltage of the power supply in the circuit.When the load of the triode is inductive load,such as transformer,coil and so on,the selection of BVCEO value should be careful.The induction voltage on the inductive load may reach 2~8 times of the power supply voltage.
Generally,the Icm of the small power triode is between 30~50mA.Generally speaking, the small signal circuit can not be considered.But for driving relays and tubes that drive high power speakers,we must calculate carefully.Of course,first of all,we need to know how much Ma is the current of the relay,so as to determine the IcM of the transistor.
The maximum allowable dissipative power Pcm of the tri electrode can be calculated by P=UXI when the current (work summary) current (the collector current) of the triode in the circuit is estimated and the voltage between the triode collector and the emitter is known.
The selection of high power triode.
For the high power triode,as long as it is not a high frequency emission circuit,it is not necessary to consider the characteristic frequency of the triode fr.for the electrode emitter reverse breakdown voltage of the tri electrode,and the limit parameter of BV-CEO is the same as that of the small power triode.The choice of the maximum allowable current Icm of the collector is also calculated according to the load condition of the triode.The maximum allowable dissipative power PcM of the triode collector is an important consideration in the high power triode.It is important to note that the high power triode must have a good radiator.Even a forty or fifty watt high-power triode can only withstand two or three watts of power dissipation without a radiator.The choice of high-power triode should also be left with sufficient allowance.In addition,when choosing the high-power triode,it should consider its installation conditions to decide whether to choose plastic or metal encapsulated tubes.
If you get a transistor and you can't find its parameters,you can guess its parameters according to its shape. At present,the small power triode is most commonly seen in the TO- 92 encapsulation pipe,and also partly in the metal shell package.Their PcCM is usually between 100~500mW,and the maximum is no more than 1W.Their Icm is usually between 50~ 500mA,and the maximum is no more than.5A.Other parameters are not well judged.