Do you know what are the precautions for using MOS tubes?
(1) A suitable heat sink must be added when using a VMOS tube. Taking VNF306 as an example, the maximum power can reach 30W after the tube is equipped with a 140×140×4 (mm) heat sink.
(2) The gate-source voltage of the junction MOS transistor can not be reversely connected and can be saved in the open state. When the insulated gate MOS transistor is not used, since its input resistance is very high, the electrodes must be short-circuited to avoid the external electric field to lead tube is damaged by the action.
(3) When using various types of MOS tubes, they must be connected to the circuit in strict accordance with the required bias, and the polarity of the MOS tube bias should be observed. For example, the junction between the source and drain of the junction MOS transistor is a PN junction, the gate of the N-channel transistor cannot be positively biased; the gate of the P-channel transistor cannot be negatively biased, and so on.
(4) When installing the MOS tube, pay attention to the location of the installation to avoid heating elements; to prevent the vibration of the tube, it is necessary to fasten the tube; when the lead is bent, it should be larger than the root size of 5 mm. To prevent bending of the pins and causing air leaks.
(5) In order to safely use the MOS tube, the limit value of the dissipated power of the tube, the maximum drain-source voltage, the maximum gate-source voltage, and the maximum current cannot be exceeded in the design of the line.
(6) After the multiple tubes are connected in parallel, the high-frequency characteristics of the amplifier are deteriorated due to the corresponding increase in the inter-electrode capacitance and the distributed capacitance, and the high-frequency parasitic oscillation of the amplifier is easily caused by the feedback. For this reason, the parallel composite tube tubes generally do not exceed four, and the anti-parasitic oscillation resistors c are serially connected to the base or the gate of each tube.
(7) When soldering, the soldering iron housing must be equipped with an external grounding wire to prevent damage to the tube due to electrification of the soldering iron. For a small amount of soldering, you can also solder the soldering iron after removing the plug or cutting off the power. Especially when soldering insulated gate MOS transistors , they should be soldered in the order of source-drain-gate, and the power should be cut off.
(8) In order to prevent the gate breakdown of the MOS tube, all test instruments, worktables, soldering irons, and the circuit itself must be well grounded; when the pins are soldered, the source is soldered first; before being connected to the circuit, All the lead ends of the tube are kept short-circuited with each other, and the short-circuit material is removed after soldering; when removing the tube from the component holder, the grounding of the human body should be ensured in an appropriate manner; if of course, The advanced gas-fired electric soldering iron is convenient for soldering MOS tubes and ensures safety. When the power is not turned off, it is absolutely impossible to insert or remove the tubes from the circuit. The above safety measures must be taken care of when using MOS tubes.
(9) For power MOS tubes, there must be good heat dissipation conditions. Because the power MOS tube is used under high load conditions, it is necessary to design a sufficient heat sink to ensure that the temperature of the housing does not exceed the rated value, so that the device can work stably and reliably for a long time.
(10) When soldering with 25W soldering iron, it should be fast. If soldering with 45~75W soldering iron, use the tweezers to clamp the root of the pin to help dissipate heat. The junction MOS tube can qualitatively check the quality of the tube by using the table resistance file (check the resistance between the forward and reverse resistance of each PN junction and the drain source), and the insulated gate field effect tube cannot be inspected with a multimeter, and the tester must be used. Moreover, the short-circuit line of each electrode can be removed after the tester is connected. When it is removed, it should be short-circuited and then removed, and the key is to avoid the gate hanging.
(11) When using the input impedance is high, it is necessary to take moisture-proof measures to avoid lowering the input resistance of the MOS tube due to temperature influence. If a four-lead MOS transistor is used, its substrate leads should be grounded. The ceramic packaged sesame tube has photosensitive properties and should be protected from light.
(12) Since the input impedance of the MOS tube is extremely high, the lead pin must be short-circuited during transportation and storage, and the metal shield package should be used to prevent the external induced potential from breaking down the gate. In particular, it is important to note that the MOS tube cannot be placed in a plastic box. It should be placed in a metal box when it is stored, and the tube should be protected from moisture.
In short, to ensure the safe use of MOS tubes, there are many things to be aware of, and the safety measures adopted are various. The vast number of professional and technical personnel, especially the vast number of electronic enthusiasts, must proceed according to their actual conditions, and take practical measures to use MOS tubes safely and effectively.
If you want to know more, our website has product specifications for MOS tubes, you can go to ALLICDATA ELECTRONICS LIMITED to get more information