The amplification ability of a transistor is one of its most fundamental properties. Generally, the transistor amplification detection jack on a digital multimeter can be used to roughly measure the amplification of the transistor The following figure shows the detection method for transistor amplification
1. For a known model and pin arrangement of a transistor, its performance can be judged according to the following method
(1) Measure the interpole resistance.
. Place the multimeter in R × 100 or R × In 1K gear, test according to six different connections of red and black pens. Among them, the forward resistance values of the emission junction and the collector junction are relatively low, while the resistance values measured by the other four connection methods are all very high, ranging from several hundred kiloohms to infinity. But whether it is low resistance or high resistance, the inter electrode resistance of silicon based transistors is much higher than that of germanium based transistors(2) The value of the penetration current ICEO of the transistor is approximately equal to a multiple of the transistor β The product of the reverse current ICBO of the collector junction. ICBO grows rapidly with the increase of environmental temperature, and the increase in ICBO inevitably leads to an increase in ICEO. The increase in ICEO will directly affect the stability of pipe operation, so pipes with small ICEO should be selected as much as possible in use By directly measuring the resistance between the e-c poles of the transistor using a multimeter, the size of ICEO can be indirectly estimated. The specific method is as follows:
The range of the multimeter resistance is generally selected as R × 100 or R × 1K gear, for PNP tubes, the black meter tube is connected to the e-pole, and the red meter pen is connected to the c-pole. For NPN type triodes, the black meter pen is connected to the c-pole, and the red meter pen is connected to the e-pole. The greater the resistance required to be measured, the better. The larger the resistance value between e-c, the smaller the ICEO of the pipe; On the contrary, the smaller the measured resistance value, the greater the ICEO of the tested tube. Generally speaking, the resistance values of medium and small power silicon tubes and germanium low-frequency tubes should be in the hundreds, tens, and tens of thousands of ohms, respectively. If the resistance value is very small or the multimeter pointer shakes back and forth during testing, it indicates that the ICEO is large and the performance of the tube is unstable (3) Measure amplification capability（ β)。 At present, some models of multimeter have scale lines and test sockets for measuring the hFE of the transistor, which can easily measure the amplification of the transistor. First, turn the function switch of the multimeter to the "" position, and then turn the range switch to the "ADJ" position. Short circuit the red and black probes, adjust the zero adjustment knob to make the multimeter pointer indicate zero. Then, turn the range switch to the "hFE" position and separate the two short probes. Insert the tested transistor into the test socket to read the amplification of the tube from the "hFE" scale line
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