I have heard them described as lateral, vertical, or linear.
And specifically if I am looking for replacements for say the K135/J50 pair, what should I be looking for in the datasheet to describe the behavior of these devices?
It seems even the recommended replacements are long discontinued.
And specifically if I am looking for replacements for say the K135/J50 pair, what should I be looking for in the datasheet to describe the behavior of these devices?
It seems even the recommended replacements are long discontinued.
Can of worms 🙂
OK, so the 2SK135 2SJ50 are Lateral FET's and are distinguished by having a very low gate turn on threshold voltage.
You need to look at Exicon products:
Exicon Lateral MOSFETS
The lateral FET's are available in single and dual die types which in simple terms means the equivalent of a parallel device increasing the maximum current from 7A to 14A.
Look for the ECF10N20 and ECF10P20
Exicon Lateral MOSFETS - Our Product Range
OK, so the 2SK135 2SJ50 are Lateral FET's and are distinguished by having a very low gate turn on threshold voltage.
You need to look at Exicon products:
Exicon Lateral MOSFETS
The lateral FET's are available in single and dual die types which in simple terms means the equivalent of a parallel device increasing the maximum current from 7A to 14A.
Look for the ECF10N20 and ECF10P20
Exicon Lateral MOSFETS - Our Product Range
This thread is from 15 years ago but it seems little has changed: Lateral MOSFET replacements for 2SK1058 (Hitachi)
Exicon, the identical Alfet brand and also Magnatech (BUZ900/905), do have some suitable replacement types for those obsolete metal can Hitachi lateral mosfets but maybe not be for long. Stocks have been unreliable for as long as I can remember but now they disappear completely before reappearing some months later. Renesas, Hitachi's successor, are down to supplying only one complementary pair in a T03P plastic case (2SK1058/J162) and even they have become scarce following the Japanese earthquake not so long ago. Note that Exicon and Alfet brands are specified in different terms like peak versus maximum continuous voltage/current ratings and this gives the impression of being different products - but look closer.
For the present, I suggest looking to plastic (TO247 or TO264) varieties of the lateral Mosfets - like EXC10N20/10P20 or ECWxxxx, if that's possible with any DIY plans you may have. That's for genuine parts and availability into the future rather than any performance concern. One thing about NOS parts that many here have learned the hard way, is not to trust the sources or resellers - the fakes industry for obsolete parts is flourishing like never before and suppliers don't seem to care one way or the other about quality.
Exicon, the identical Alfet brand and also Magnatech (BUZ900/905), do have some suitable replacement types for those obsolete metal can Hitachi lateral mosfets but maybe not be for long. Stocks have been unreliable for as long as I can remember but now they disappear completely before reappearing some months later. Renesas, Hitachi's successor, are down to supplying only one complementary pair in a T03P plastic case (2SK1058/J162) and even they have become scarce following the Japanese earthquake not so long ago. Note that Exicon and Alfet brands are specified in different terms like peak versus maximum continuous voltage/current ratings and this gives the impression of being different products - but look closer.
For the present, I suggest looking to plastic (TO247 or TO264) varieties of the lateral Mosfets - like EXC10N20/10P20 or ECWxxxx, if that's possible with any DIY plans you may have. That's for genuine parts and availability into the future rather than any performance concern. One thing about NOS parts that many here have learned the hard way, is not to trust the sources or resellers - the fakes industry for obsolete parts is flourishing like never before and suppliers don't seem to care one way or the other about quality.
Linearity and mosfets are not usually associated with each other. That being said, lateral types tend to trek toward the inverse square law in relation to transconductance. (Gm) Kind of like Jfet or kind of triody, sort of. 🙄 Vertical type devices tend to lean towards an exponential Gm. Generally speaking, vertical types have a much greater conductance than lateral type. Both types, more acute in vertical, is a drop in Gm at lower currents and this effectively produces a crossover distortion component. So for class AB, push pull bias, this can be a problem so usually bias is turned up about an order above a similar typical Bipolar configuration. A very large difference is that at these lower bias levels the vertical types require thermal compensation similar to Bipolar. Lateral devices can be bias with a simple resistor due to a different temperature co-efficient of the two different types of mosfets.
Of the vertical types, there are different architectures. Hexfet is more like many individual mosfets in parallel on the same die or a plural well device. Another type is planer stripe. The structure more resembles a singular well. Planer stripe fets seem to handle a greater peak power it seems, so is my experiments in mosfets amplifiers.😀. This comes with an extra penalty of nonlinear relation of Gm to Vds but they can certainly be used if used properly. 😉 Power handling really depends on how well the heat is spread out across the die and that it doesn't concentrate in one area, burning it up there. This is known as hot-spotting. Usually this is the executioner of Bipolars as they approach second breakdown.
Then came along Trench fets. These are most suited for switching as they have very high conductance and thus lower Ton losses. They do not handle linear power very well and are not used for linear output stages on account of they tend to hot-spot. One issue with Trench fets is that in the ON state, the electric field may overlap with the drain section and require more gate charge to turn off. A new type called Nexfet is similar but slightly different architecture to prevent this problem. As for linear output stages using vertical fets, Hexfet and planer stripe fets are suitable.
Then came along Trench fets. These are most suited for switching as they have very high conductance and thus lower Ton losses. They do not handle linear power very well and are not used for linear output stages on account of they tend to hot-spot. One issue with Trench fets is that in the ON state, the electric field may overlap with the drain section and require more gate charge to turn off. A new type called Nexfet is similar but slightly different architecture to prevent this problem. As for linear output stages using vertical fets, Hexfet and planer stripe fets are suitable.
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