minions
Meter Reader 1st Class
Posts: 99
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Post by minions on Oct 30, 2009 12:06:16 GMT -5
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Post by JohnH on Oct 30, 2009 14:48:05 GMT -5
1 is a Junction Field Effect Transistor (JFET), one of my favorite devices. They are great for forming buffers and gain stages in preamp and overdrive circuits. They operate a bit like a valve, where the current that flows from top to bottom is determined by the voltage on the leg with the arrow. It has very high input impedance. 2 is a capacitor, and the curved / flat lines indicate that it is polarised, meaning that one side (the flat one) has to be +. Hence usually an electrolytic type, but functionally it does the same as any other capacitor. 3 Is a type of Metal Oxide Field effect transistor(MOSFET). Like 1, but with even higher input impedance, and sensitive to being zapped by static until connected into a circuit. I haven't used these, but here is more than you want to know..... MOSFETsJohn
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Post by gumbo on Oct 30, 2009 23:57:45 GMT -5
Thanks for that, too, John..... ...probably was/is more than I needed to know but you've certainly given me something to contemplate... ...I think I understand them all a bit better now...trouble with that is, I then start thinking of ways to use all this stuff and add another ten projects to the already-full list ;D
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Post by sumgai on Oct 31, 2009 2:55:53 GMT -5
Actually, the drawing shown for the capacitor is the standard symbol recognized and accepted by both the IEEE and the IEC. The curvature is the way it's been drawn almost since the dawn of electricity. When one needs to polarize it (to denote an electrolytic), one adds a plus sign in close proximity to the straight line.
John has the other two correctly identified. But be aware that sometimes you'll see the incoming line (with the arrow) on the JFET in the center, not towards the bottom - either way is acceptable, and means the same thing. Also, the arrow may point outwards - that denotes the opposite polarity, but otherwise it's the same thing.
Too, the MOSFET may have the arrow on the lower leg instead of the center, and the arrow may be pointing outwards. Both conditions apply the same as for the JFET.
HTH
sumgai
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