Main parameters of the hottest triode

2022-08-06
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The main parameters of triode

the parameters of triode reflect various performance indicators of triode, and are the basis for analyzing triode circuit and selecting triode

I. current amplification factor

1. common emitter current amplification factor

(1) common emitter DC current amplification factor, which represents the ratio of DC current IC to IB at a certain working point when the triode is connected to the common emitter. When Icbo is ignored,

(2) common emitter AC current amplification factor β It represents the change of collector current when the triode is connected with common emitter and uce is constant Δ IC and base current variation Δ Ratio of IB, i.e.

of pipe β If the value is too small, the amplification effect is poor; β When the value is too large, the working performance is unstable. Therefore, generally β 30 ~ 80 pipes

2. common base current amplification factor

common base DC current amplification factor, which represents the ratio of IC to ie at a certain operating point when the triode is connected with a common base.

(2) common base AC current amplification factor when Icbo is ignored α, It refers to the ratio of IC and ie changes when the triode is connected as a common base and the UCB is constant, that is:

usually the Icbo is very small. Therefore, it is often mixed without distinction in practical use

II. Inter electrode reverse current

1. set base reverse saturation current icbo

icbo refers to the reverse current corresponding to the open emitter circuit and a certain reverse voltage is applied between the collector and the base. It is the drift current of the minority carrier. Icbo is a constant at a certain temperature. Icbo will increase with the increase of temperature, which is the main factor for the instability of triode. At the same ambient temperature, the Icbo of silicon tube is much smaller than that of germanium tube, "said one company official

2. penetration current iceo

iceo refers to the collector current when the base is open and a certain reverse voltage is applied between the collector and the emitter. The relationship between ICEO and Icbo is:

the current seems to pass from the collector to the emitter, so it is called penetrating current. ICEO, like Icbo, is also an important parameter to measure the thermal stability of triodes

III. frequency parameter

frequency parameter is a parameter that reflects the relationship between the current amplification ability of the triode and the working frequency, and represents the frequency application range of the triode

1. common emitter cut-off frequency f β

triode β Value is a function of frequency, if band β=β O almost independent of frequency, but as the frequency increases, β Value decreases. Under the support of national "863" program and Natural Science Foundation of China β Value drops to intermediate frequency band β When O1/root is 2 times, the corresponding frequency is called the common emitter cut-off frequency, using f β Indicates

2. characteristic frequency ft

when the β Value drops to β= The frequency corresponding to 1 is called the characteristic frequency. We will introduce f β~ Within the range of FT, β The value is almost linear with F, and the higher F, β The smaller, when the operating frequency f> ft, the triode will lose its amplification ability

IV. limit parameter

1. the maximum allowable collector dissipation power pcm

pcm refers to the maximum power dissipated by the collector when the transistor parameter change caused by the heating of the triode collector junction does not exceed the specified allowable value. When the actual power consumption PC is greater than PCM, it will not only change the parameters of the tube, but also burn the tube. PCM can be calculated by the following formula:

pcm = ICUCE gs0126

when the PCM of the tube is known, the PCM curve can be drawn on the output characteristic curve by using the above formula

2. maximum allowable collector current icm

when IC is large, β The value decreases gradually. The general rule is that β When the value drops to 2/3 (or 1/2) of the rated value, the corresponding collector current is ICM. When IC > ICM, β The value has been reduced to an impractical level, and there is the possibility of burning the pipe

3. reverse breakdown voltage BVCEO and bvceo

bvceo refer to the reverse breakdown voltage between collector and emitter when the base is open circuit

bvcbo refers to the reverse breakdown voltage between the collector and the base when the emitter is open circuit. In general, BVCEO (0.5 ~ 0.8) bvcbo of the same pipe. The reverse working voltage of the triode shall be less than (1/2 ~ 1/3) of the breakdown voltage to ensure the safe and reliable operation of the tube

there are few reports on the influence of the three limit parameters PCM of the triode, especially the grain size on the small crack propagation. The area surrounded by ICM, BVCEO and the critical saturation line and cut-off line mentioned above is the linear amplification area for the safe operation of the triode. Generally, triodes used for amplification must work in this area. (end)

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