Q & A about HFE of HG2879
We mark HFE on the lid of HG2879. After testing by customer they always have following question.
1) HFE Scope about HG2879.
Some customer hopes to get higher HFE HG2879 so that the part can output more power. In this case, please let us know before shipping. The main HFE scope is 50-70. Only very very few can reach 80. Never did see the HFE can reach 85.
2）There is some gap between HFE customer test and HFE we mark
Many USA customer use simple testing equipment such as DCA75 to test HFE. This type of simple tester can't get the right HFE. Please see the testing condition of DAC75 from DCA75 specification as follows.
The HFE testing condition is 5ma/3V or 5ma/9V. But if you look at the datasheet of 2SC2879, the testing condition should be 10A/5V. Actually, the DCA75 only use one battery. It is not difficult to understand the battery can't provide such testing condition. The HFE are different if we use different testing condition. That’s why you find HFE is 43 or 45, but the HFE we mark is 70.
In order to describe the problem more clearly, we use different HFE testing condition to test 6 PCS 2SC2879. Please refer to following photo. You can see the HFE of each 2SC2879 at 5mA/5V, 10mA/5V, 50mA/5V, 100mA/5V, 1A/5V, 5A/5V and 10A/5V.
From the photo above, we can see if we use 5mA/5V to test the 6 HG2879. The HFE scope is 37-39. But if we use 10A/5V to test the 6 HG2879, the HFE scope is much higher. It is 64-66.
3) I use DCA75 to test HFE of the matched parts HG Company provided. But the HFE DCA75 I gets are not same.
For example, customer gets 4 PCS HG2879 whose lids are mark 70 as HFE. But when he uses DCA75 to test, he finds HFE differs from 43 to 45. His question is why the HFE DCA75 gets are not totally same.
Yes, they are different. It is right. Please check the HFE of No5 and No6 in the photo above. The HFE(10A) of No5 is higher than No6, but the HFE(5mA) of No5 is lower than No6. Normally, if HFE(10A) is higher, the HFE(5mA) will also be higher. But it is not always fixed. That's why we have to test HFE using the right testing current and voltage.
Please believe our testing data. We use DTS1000 testing system to test HFE of each part. DTS1000 system comes from Japan. It is very expensive. The testing data is very accurate.
4) Why there is some 1-3 gap when we test the same transistor at different time.
Because the temperature of environment impacts the HFE testing result. Normally, if the temperature increases 1 degree, HFE increases 0.5%-1%. Normally, the temperature of workshop is fixed. But we can’t ensure the temperature is totally same anytime and anywhere in our workshop.
In normal case, the parts in one shipment you get are tested together. In this way, average error can be less. But if you get HG2879 from different lot, there may exists 1-3 gap in HFE. I don’t think 1-3 HFE gap may impacts performance obviously.