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This is a snippet of the data sheet of the BJT transistor 2SC828A. enter image description here

  1. What do they mean by Q R and S classifications?

  2. I know that 2 in the code means transistor. What do the other numbers and letters mean (SC828A)?

Link to the data sheet:

2SC828A data sheet

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  • \$\begingroup\$ People will be more likely to give you an answer if you give us a link to the full datasheet. \$\endgroup\$ – The Photon Sep 10 '16 at 1:12
  • \$\begingroup\$ The BC548 is a BJT and it doesn't have the front 2. But the 2N2222 is a BJT. \$\endgroup\$ – Bradman175 Sep 10 '16 at 3:23
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[...] BJT transistor 2SC828A

  1. What do they mean by Q R and S classifications?

These are the different ranges of \$h_{FE}\$ values, as shown in your original question, which each of those transistors could have. Look on the transistor for one of the letters Q, R or S often marked just underneath an abbreviated part number like 828A.

If the transistor has no such letter Q, R or S marking (sometimes called a Current Gain Group) then all you know (without measurement) is that its \$h_{FE}\$ value should be within the limits shown on the datasheet. Your linked datasheet shows the \$h_{FE}\$ minimum = 130 and maximum = 520:

hfe minimum and maximum from original datasheet

As expected, those values fit with the lower and upper limits of those classifications/groups.

  1. I know that 2 in the code means transistor. What do the other numbers and letters mean (SC828A)?

This is the JIS marking standard. In the case of the 2SC828A, they mean:

  • SC = NPN HF bipolar transistor
  • 828 = the JEITA-EDEREC number assigned to this type of transistor originally; the individual digits have no additional meaning
  • A = a later version than the original (i.e. the one without any letter suffix); multiple versions are possible for some devices e.g. B, C suffixes etc.

    The general rule is that you can safely replace an earlier suffix letter device, with a later one (e.g. you can replace a 2SC828 with a 2SC828A) but not vice versa.

    (Same thing applies with the 2N2222 and 2N2222A, for example, where the 2N2222A has some improved maximum voltage ratings. However the meaning of a suffix can vary; if in doubt, find better datasheets for that device which explains them.)

For this particular transistor, the "A" suffix versions have some improved voltage ratings, as shown in this datasheet which covers both the 2SC828 and 2SC828A. The differences are summarised as:

differences between 2SC828 and 2SC828A from datasheet

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Let's dissect the word 2SC828A...

2

This is part of the Japanese Industrial Standard where they denote the markings of transistors with 2SC, 2SA and more. The "2" like you said means it's a transistor (where "1" means diode).


SC

Again part of the JIS, the "SC" stands for NPN high frequency transistor.


828

So far I am unable to tell a pattern between the 3 numbers and the other characteristics. All I know is that if the number is different from another 2SC transistor, some characteristics would vary.


A

The A in 2SC828A denotes the voltage rating of the transistor. Generally, higher values like B and C have higher voltage ratings. Like the TIP35C.


But wait... There is an extra letter that will show up on your transistor. So your transistor will actually say something like, 2SC828AQ, 2SC828AR or 2SC828AS, being 3 variants of 2SC828A. This explains your question with the Q/R/S part of the hFE shown in your datasheet.

The suffix your transistor has determines which hFE gain it will have, as concluded from the datasheet.

  • Q in 2SC828AQ has a hFE of 130-260.

  • R in 2SC828AR has a hFE of 180-360.

  • S in 2SC828AS has a hFE of 260-520.

These suffix letters are also Hfe ranks. See here.


Source: http://www.transparentsound.com/transistors/vintage-transistors/JIS/jis01.htm

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You can look at this link for an explanation of the hFE ranking.

http://engineering.rohmsemiconductor.com/index.php?/Knowledgebase/Article/View/1/1/what-is-the-transistor-hfe-ranking

In case the link does not work anymore! Here some further information. The ranking code is mentioned as a suffix after the basic partnumber. hFE Ranking Codes hFE Range A 16 - 32 B 25 - 50 D 60 - 120 E 100 - 200 F 160 - 320 M 39 - 82 N 56 - 120 P 82 - 180 Q 120 - 270 R 180 - 390 S 270 - 560 E 390 - 820 U 560 - 1200 V 820 - 1800 W 1200 - 2700 The complete number would be 2SC828A (suffix R,Q,S) The suffix A indicating the voltage range.

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  • \$\begingroup\$ Please summarize the relevant information so that your answer will still be useful if the linked document changes or is removed. \$\endgroup\$ – The Photon Sep 10 '16 at 1:15

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