Transistor circuit of a pressure gauge


Posted on Mar 28, 2007

In order to ensure that the transistor in the circuit to work properly, it is often the reverse breakdown voltage of the transistor to be measured.


Transistor circuit of a pressure gauge
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Especially for the requirements of the reverse breakdown voltage of the tube is relatively high, such as tubes OCL power amplifier of the differential amplifier, is greater than the reverse breakdown voltage requirements tens of volts. Available transistor withstand voltage test circuit testing. TV video amplifier tube output and line output, requiring more than a hundred volts, the need to measure up. Figure 5-23a pressure test is a simple transistor circuit which is capable of measuring crystal diode, the breakdown voltage of the transistor buildings, but also to test crystal regulator regulation characteristics of the tube. Said hatch circuit: the diode is reverse voltage, reverse current is very small. But increasing reverse voltage to a certain value when the reverse current increases rapidly, the tube into the reverse breakdown state, as shown in Figure 5-23b. After entering the tube to the breakdown state, the current through the tube, mainly depends on the external circuit, the external circuit if the current measure poured limited, the current will be large, there is danger of burn out of the tube. The reverse breakdown voltage of the transistor is reflected in the breakdown characteristics. It refers to the reverse current reverse voltage reaches a certain predetermined value. This anti predetermined value to the current can be isolated from the transistor characteristics table test conditions. In the circuit of Figure 5-23, the transformer into the AC voltage 220V to 250V AC voltage through the diode rectifier and capacitor filter, to obtain 300V DC high voltage. When the load voltage is lower. Voltmeter used to measure the reverse breakdown voltage of diode or transistor, diode or crystal ammeter to monitor pension tube reverse current. (1) measurement of high-power tube BVceo when single-pole double-throw switch S to position "high-power" at the high-power diode can be measured or crystal transistor anti Koh breakdown voltage. 3AD30 such as measuring the collector-emitter breakdown voltage BVceo, ammeter into gear with 50mA, the circuit shown in Figure 5-22c. R1 and RP1 composition limiting resistor. From the transistor characteristics can be found in the table '. The test conditions 3AD30 BVceo anti currents to 20mA. Adjust RP1, ammeter pointer falls at 20mA. At this time, the voltage meter reading is made this tube collector -emitter reverse breakdown voltage. If the measured reverse breakdown voltage BVceo. Base emitter resistors an extremely indirect regulations. For example, the measured 3AD30 BVceo, to resistor 20fz so. (2) measurement of small power tube BVceo when single-pole double-throw switch S to position "small power" at the low-power diode can be measured or crystal tube reverse breakdown voltage. 3DG6 such as measuring the collector-emitter breakdown voltage, circuit ammeter selection 500riA file, the circuit shown in Fig. 5-23d, foot-2 and RP2 composition limiting resistor use high resistance voltmeter voltmeter. From the transistor characteristics can be found in the table, the BVceo 3DG6 test conditions reverse current lOOyA. Adjust RP2 ammeter pointer falls 100VA place. At this time, the high-voltage resistance meter reading is this tube collector emitter reverse breakdown voltage poles. Regulators Features (3) the amount of rinse regulator regulator when measured, S also to position "power" place. In addition to reading from the voltmeter Zener voltage outside, adjust RP1, it can also measure the voltage characteristics of the regulator in a few milliamperes to 20mA. (4) Component selection commercially available transformer power transformer. Available rectifier diode voltage is greater than 300V, the forward current is greater than 2CP lOOmA type of pipe. When measuring high-power tube, with a simple voltmeter multimeter voltage profile on it. But when measuring low-power tube, be sure to use a high internal resistance voltmeter, such as 20kfl per volt voltmeter or use a simple transistor voltmeter, otherwise it is not measured out.




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