Hfe what is

Other circuits are deliberately designed to not be sensitive to hFE or hfe. The Big Muff Pi is an example of this. At the beginning of this article, I said we have to supply base current to get collector current flowing. That's only partially true because many germanium transistors, especially vintage ones, are leaky enough to supply their own base current. There's still base current, but it's coming from inside the transistor instead from the circuit outside the transistor.

All three stages of the Maestro FZ-1 and its variants are examples of leakage biasing. This leakage current makes measuring hFE more difficult because we have to account for the effects of leakage current. Real transistor testers, like the DCA55, make the measurement correctly.

Variability in leakage and hFE are why some modern germanium fuzz circuits have trimpots in them. When Steve Daniels at Small Bear sells a matched set of Tonebender or Fuzz Face transistors, he also includes the biasing resistors for that set.

Those resistors are part of the matching and accommodate the part-to-part variability in the transistors. So how do you know you have the right hFE or hfe? If you're substituting transistors or building with germanium, use sockets and plan on trying a few different ones. Last edited: Nov 9, I was long overdue for this refresher. Thanks Chuck!

This is a great initiative for people like me who like to build, but only have a basic grasp of this stuff. Will make for nice reading material during the winter months here. Barry Well-known member. HamishR Well-known member. And speaking of BJT current ratings, how much can a bipolar bear? Chas Grant Well-known member. HamishR said:. Click to expand Last edited: Nov 3, Dang, Chuck.

As a result of the manufacturing processes, bipolar transistors typically have a wide range in their values of current gain. Often figures for both parameters are specified.

When giving the specification, the test conditions are outlined. The current level and collector emitter voltage are normally specified.

In view of the spread of current gain levels in these electronic components, figures for minimum, typical and maximum may be given.

Often, not all of these figures are give: sometimes only the minimum figure for the current gain may be specified. As there can be a significant variation in gain for a given type of transistor, a suffix letter on the end of the transistor part number may specify the band of gain expected for that particular device. Whatever the circuit used, and whether NPN transistors or PNP transistors are used, the current gain of the transistor is a key parameter. Although there are significant gain variations, most circuits are tolerant to the actual gain of the transistor, requiring it to be sufficient to ensure correct operation.

BC Plastic leaded transistor Normally current gain specifications for transistors normally have a very wide tolerance, and therefore circuits need to be able to accommodate this. This is the forward current gain for the transistor when operated in a common emitter mode. Most of these devices draw their power from tiny batteries. Most spacecraft also rely on microchips, and thus transistors. By far the most common application of transistors today is for computer memory chips—including solid-state multimedia storage devices for electronic games, cameras, and MP3 players—and microprocessors, where millions of components are embedded in a single integrated circuit.

Transistors are a three terminal semiconductor device used to regulate current, or to amplify an input signal into a greater output signal. Transistors are also used to switch electronic signals. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. HFE gene homeostatic iron regulator.

From Genetics Home Reference. Normal Function The HFE gene provides instructions for producing a protein that is located on the surface of cells, primarily liver and intestinal cells. More About This Health Condition. Hereditary hemochromatosis Researchers have identified more than mutations in the HFE gene that cause type 1 hemochromatosis, a form of hereditary hemochromatosis that begins during adulthood.

X-linked sideroblastic anemia The CysTyr mutation, which is a common cause of type 1 hereditary hemochromatosis described above , may also increase the severity of the iron overload in X-linked sideroblastic anemia when it is inherited along with a mutation in the ALAS2 gene. References Andrews NC. Molecular control of iron metabolism. Best Pract Res Clin Haematol. HFE gene: Structure, function, mutations, and associated iron abnormalities.

Epub Oct 9. Porphyria cutanea tarda: multiplicity of risk factors including HFE mutations, hepatitis C, and inherited uroporphyrinogen decarboxylase deficiency. Dig Dis Sci. Iron Imports. HFE and regulation of intestinal iron absorption. Iron sensing as a partnership: HFE and transferrin receptor 2. Cell Metab.