How to replace the transistor?
Why do people have a question about how and with what it is possible to replace a transistor? It arises due to the fact that it happens that when working with something or when repairing an item, for example, when repairing an impulsive power supply, it happens that the store does not have the necessary fieldistor that has been broken. The master is forced to look for a way out, because he is obliged to fix it in time. Therefore, this person begins to look for analogues, those that are available.
It even happens that the device that was before simply stopped being produced, at least delivered to your city. And, of course, there are no other options, just trying to find an analogue, but this is not the easiest task, in fact. You need to be able to look at the parameters of each such item, and only then make a choice in favor of one.
What kind of transistors can be replaced?
To begin with, we will analyze bipolar transistors, the most common. The most important thing to know about them:
- the first step is to find out what is its maximum voltage;
- after which you need to check how things are with the collector current;
- then finding out how much power is dissipated, and what is the frequency;
- and finally, how the current is transmitted.
First, of course, you need to start by evaluating the characteristic in general. The most important and first steps will be: finding out the frequency and speed. It will be very good if the frequencies are different, that is, the operating frequency will be less than the cutoff frequency. This will make everything function better.
Well, if it is the other way around, and the working frequency with the boundary will be practically at the same frequency, then in this case an incredibly large amount of energy will be needed, since the current transfer coefficient will have its own specific goal, it will go to 1. Therefore, it is necessary that the cutoff frequency of the analog you are picking up was equal to the frequency of the item that was before. But you can make it so that the frequency is higher.
Next, be sure to pay attention to power. That is, you need to find out the maximum collector current and collector-emitter voltage. The maximum collector current must be much higher than the current of this device. With voltage, on the contrary, the working device should have it higher.
Watch a video on how to replace Soviet radio components.
If you use a datasheet to search for an analogue, then, of course, it is important to understand that all analogue indicators must correspond to the previous device, it would be nice even if they were superior.
For example, if there was a problem with the transistor, and the collector-emitter voltage was about 80 volts, and the current was 10 amperes, then, according to the data, it should be 15 amperes in current, and about 230 volts in voltage. And this analogue will go for a complete replacement.
For example, very often 2N3055 is replaced by KT819GM, and these semiconductor components can easily replace each other. If we talk about the similarity of these amplifiers, then both of them are considered an ideal replacement for each other and will come out quite effective, and they will not bring any special problems.
Also very common components today. They are used even more often than bipolar. For example, inverters are now mostly only with field ones, that is, they have already constrained bipolar devices. And if you have a question, is it possible to replace a field-effect transistor with a bipolar one, then the answer will be yes. However, in the field there are much more advantages than in the bipolar one.
Field amplifiers absorb much less energy than bipolar ones, since field amplifiers focus on the voltage and electric field of the charge, while bipolar ones are kept on the base current. Therefore, they are more preferred. Field-effect transistors even switch many times faster than bipolar ones. In addition, they have good thermal stability. And in order to switch the direction of electric current, field-effect transistors can be connected in parallel and without resistors, you just need a driver suitable for this.
If we talk about replacing field triodes, then here there is a way to search for their analogues. In principle, in search with bipolar it is not much different, one can even say that it will be almost the same. But there is a small difference: there is no problem with current transfer, like a bipolar transistor. We must not forget about the drain-source, you need to remember about the stock.
In addition, the field has such a parameter as the resistance of an open channel. From him it is easy to determine what will happen to the power, and how it will be dissipated. And, of course, it is very important to calculate this open channel resistance, since you can lose a lot of energy and the voltage during the transition will not be too high.
What can replace field effect transistors?
The steepness S is also very important when looking for an analogue. This parameter will show the status of drain current at gate voltage. This will determine how much voltage is needed for switching.
Remember that it is also important to choose based on the gate threshold voltage, if the voltage is several times less than the threshold voltage, then you will not have to wait for normal operation from your analog. The circuit, when receiving voltage, will not receive the necessary power and all the power, or rather its dissipation, will remain on the device, and this is undesirable for it, because overheating can occur.
The datasheet also says that the power dissipation of both devices is the same: and it depends on the case. If the case is large, then the heat output will be safely dissipated.
Gate capacitance is also very important in this case. It is very important that the shutter is not extremely heavy, and you need to keep this in mind when choosing. It will be very good if it is several times smaller, as this will bring convenience and ease of use of this mechanism. However, if you do not need to solder, then you can safely choose the size that fits perfectly, similar to the original.
For example, now quite often they change the IRFP460 to a newer and more modern 20N50, since its shutter is extremely light. Again, the datasheet will say the same thing, pointing out a lot of similarities, despite the advantage of the second.