transistor 3

Figure 2 (b) shows the input characteristic curve of the transistor, which represents the relationship between Ib and Ube. Its characteristics are: 1) When Uce is in the range of 0-2 volts, the position and shape of the curve are related to Uce, but when Uce is higher than 2 volts, the curve Uce is basically independent. Usually, the input characteristic can be represented by two curves (I and II).diode

2) When Ube<UbeR, the segment of Ib ≈ O (0~UbeR) is called the "dead zone". When Ube>UbeR, Ib increases with the increase of Ube. When amplified, the transistor operates in a more straight segment.diode

3) The input resistance of a transistor is defined as:

Rbe=(△ Ube/△ Ib) Q point, and its estimation formula is:

Rbe=rb+(β+1) (26 millivolts/Ie millivolts)diode

Rb is the base resistance of a transistor, and for low-frequency low-power transistors, rb is approximately 300 ohms.

2. Output characteristics diode

The output characteristic represents the relationship between Ic and Uce (with Ib as the parameter). As shown in Figure 2 (C), the output characteristic is divided into three regions: cutoff region, amplification region,diode  and saturation region.diode

When Ube<0 in the cutoff region, Ib ≈ 0, and there are no electrons injected into the base region in the emission region. However, due to the thermal motion of molecules, a small amount of current still passes through the collector, i.e. Ic=Iceo, which is called the penetration current. At room temperature, Iceo is about a few microamperes, and germanium tubes are about tens of microamperes to hundreds of microamperes. Its relationship with the reverse current Icbo of the collector electrode is:diode