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I studied MOSFET from ' Electric Devices and Circuit Theories by Robert L. Boylestad ' The symbols of depletion type and enhancement type MOSFET are given below from the book.
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But recently, in the book of Sedra/Smith named Microelectronic Circuits, I have found that the symbol of enhancement type is similar to the symbol of depletion type of Boylestad's book.
enter image description here

I've seen in the datasheet of many MOSFET that the enhancement type symbol is like the Boylestad's book. enter image description here

Which one is correct?

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    \$\begingroup\$ I'm not sure there are symbols to distinguish between enhancement and depletion to be honest. It's more of a MOSFET which is usually enhancement vs a JFET which is always depletion. It never even occured to me that the difference between 6.30 and 6.39 might actually mean something \$\endgroup\$ – DKNguyen May 1 '20 at 18:21
  • \$\begingroup\$ @DKNguyen Yes it is common that whatever area of electronics you are into, you only see certain types of FETs being used. \$\endgroup\$ – Justme May 1 '20 at 18:43
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To really check on what really is the correct symbol for what, you should refer to particular standards.

Below is what the IEEE 315-1975 standard (which can easily be accessible online if you look on Google) tells us, for an example...

enter image description here

enter image description here

(the IEC label nearby also indicates that it's ubiquitous to IEC standards as well)

You can claim that this is old information, and it is (frankly, I'm surprised how they don't update this standard). However, it's the most recent document that we have on this.

So which one is right? Well... Technically they're all correct and it depends what standard you're following. The Sedra/Smith textbook is not wrong because it's showing a different type of transistor symbol that doesn't show too much bulk (or substrate) activity, except for Figure 5.19a, which shows the arrow pointing outward on the P-channel FET.

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There is no right or wrong way. For a given type of FET there are many different symbols. When you make a book, you have to select a symbol and stick to it, sometimes it is a personal preference, or something the book author has learnt during his studies.

The symbols used by Boylestad seem to be more commonly used.

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