Crystal triode HFE tester without header, Hef Tester
Keywords: crystal triode HFE tester without header indication
Crystal triode HFE tester without header indication
Crystal transistor (NPN or PNP type) DC amplification of HFE is the most basic measurement parameters of the triode. Therefore, many digital multimeters can test the HFE of the triode. Here, the reader introduces a triode NPN or PNP-type HFE parameter tester that does not have a header display, which is simple, and it is very suitable for beginner electronic technicians, its test circuit. As shown in the drawings.
1. Circuit work principle
In the drawing circuit, insert the quenched tripathode (NPN or PNP type) into the transistor socket, at this time, the current supplied by the voltage of the m-point, by the collector resistance RC1 or RC2, RP of the protruded arm of the protruding arm through the switch S1a. The switch S1b, the tube base resistor RB1 or RB2 to B-E form a bias current. The op amp IC1A is connected to a buffer output (magnification equal to 1). The buffer shifts the base voltage of the tube to the same phase end of the op amp, at this time, the IC1b is maintained at a certain value between the power supply partial pressure and the tube base potential. Test. Simply adjust the potentiometer RP so that the buck on RC1 (or RC2) is equal to the voltage between the collector-base poles of the tube. When the condition is satisfied, one LED in the figure illuminates: another LED off (determined by the inserted NPN or PNP tube), once the condition is not satisfied, the LED is turned off (note: the IC1B here is in the open-loop working state) of).
When the above test conditions are satisfied. The following formula is established:
Be
2. Test Methods
The HFE tester can measure the NPN type or PNP type two triode, and the type of the triode is selected by the switch S2 in accordance with the switch S2. Test the value of the HFE two gears: Synchronous shift selection by the switches S1a and S1B: When the switches S1a, S1B is placed in a, C point (RC1, RB1 is 100Ω), at this time, the maximum value can reach 100, At B, D point (RC2, RB2 is 1kΩ), the HFE maximum is 1000, before the test, the HFE should be calibrated by the potentiometer. The calibration method is as follows: the potentiometer (100kΩ) should be selected. In order to display the HFE value, the disk is attached to the potentiometer shaft, and the knob is fixed on the shaft head. It is seen from the above formula to HFE proportional to the RB (RC setting), so the magnification of the triode is linear. To this end, calibration can be calibrated with a triode having a large multiplier (HFE), and then the triode can be tested on the socket. When the test is tested, the RP is rotated as long as LED1 (corresponding NPN-type tube) or LED2 (corresponding PNP tube) is shown by as bright, the potentiometer knob arrow indicates the HFE value of the triode.
In the test, the NPN tube, if the potentiometer primary resistance value is too large, the LED1 will be bright; too small, LED2 will be bright. For the PNP tube, the above phenomenon is just the opposite. Therefore, it is static (ie, no triode), the potentiometer knob should be good in the appropriate intermediate position.
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