Discrimination of polarity and quality of transistor pins 4

(5) Identification between high-frequency and low-frequency tubes

Distinguishing between high-frequency and low-frequency tubes: The cutoff frequency of high-frequency tubes is greater than 3 MHz, while the cutoff frequency of low-frequency tubes is 3 MHz lower. Generally, the two cannot be used interchangeably. Due to the different models of high and low frequency tubes, when their specifications are clear, diode they can be easily distinguished by referring to relevant manuals. When their logo models are unclear, BVebo can be used to measure the reverse resistance of the emitter junction with a multimeter to distinguish between high and low frequency tubes.diode

Taking NPN type tube as an example, place the multimeter in the R × lk position, connect the black probe to the emitter junction e of the tube, and connect the red probe to the pole b. At this time, diode the resistance value is generally above several hundred kiloohms. Next, pull the multimeter to the R × lOk high blocking position, with the red and black gauge strokes unchanged, and re measure the resistance value between e and b. If the measured resistance value does not change significantly from the first measured resistance value, it can be determined that the tested tube is a low-frequency tube; If the resistance changes significantly, exceeding 1/3 of the multimeter's full capacity, it can be basically determined that the tested tube is a high-frequency tube.diode