Bipolar junction transistor -History Basic operation of BJt E(p-type) B(n-type) c(p-type) (2) X(3) Schematic current flows in pnp BJT 「8 (1)Hole particle current from E to B (2) Electron particle current from b to e (3)Recombination current in B (4)Hole particle current originating in E and reaching C (5Reverse electron particle current from C to B (6)Reverse hole particle current from B to C (What is difference between"current and"particle current?) OE F Schubert, Rensselaer Polytechnic Institute, 2003
© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 1 Bipolar junction transistor - History Basic operation of BJT (1) Hole particle current from E to B (2) Electron particle current from B to E (3) Recombination current in B (4) Hole particle current originating in E and reaching C (5) Reverse electron particle current from C to B (6) Reverse hole particle current from B to C (What is difference between “current” and “particle current”?)
Qualitative basic operation of BJts What is a bjt? A BJT consists of two back-to-back p-n junctions The middle region, the base, is very thin The three regions are the emitter, base, and collector Carriers are injected (emitted) into the base from the emitter Since the base is thin most carriers injected into base diffuse into collector What does a thin base thickness "mean Base thickness is much thinner than the diffusion length of carriers injected from the emitter OE F Schubert, Rensselaer Polytechnic Institute, 2003
© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 2 Qualitative basic operation of BJTs What is a BJT? A BJT consists of two back-to-back p-n junctions. The middle region, the base, is very thin. The three regions are the emitter, base, and collector. Carriers are injected (“emitted”) into the base from the emitter. Since the base is thin, most carriers injected into base diffuse into collector. What does a “thin base thickness” mean? Î Base thickness is much thinner than the diffusion length of carriers injected from the emitter
History of point-contact transistor The first transistor was a point-contact transistor The first point-contact transistor John Bardeen, Walter Brattain, and william Shockley Bell Laboratories, Murray Hill, New Jersey (1947) Spring Emitter Bardeen Brattain Collector Base Shockley OE F Schubert, Rensselaer Polytechnic Institute, 2003
© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 3 History of point-contact transistor The first transistor was a point-contact transistor
Model of transistor in bell labs museum Museum is located at 600 Mountain Ave. Murray Hill, New Jersey OE F Schubert, Rensselaer Polytechnic Institute, 2003
© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 4 Model of transistor in Bell Labs museum Museum is located at 600 Mountain Ave., Murray Hill, New Jersey
History of the first transistor The first transistor was about half an inch high. Before Brattain started John Bardeen told him that they would need two metal contacts within 0.002 inches (0.002 inches 50 um) of each other-about the thickness of a sheet of paper. But the finest wires then were almost three times that width and couldn 't provide the kind of precision they needed. Instead of bothering with tiny wires, Brattain attached a single strip of gold foil over the point of a plastic triangle With a razor blade, he sliced through the gold right at the tip of the triangle. Voila: two gold contacts just a hair width apart The whole triangle was then held over a crystal of germanium on a spring, so that the contacts lightly touched the surface. The germanium itself sat on a metal plate attached to a voltage source. This contraption was the very first semiconductor amplifier, because when a bit of current came through one of the gold contacts, another even stronger current came out the other contact OE F Schubert, Rensselaer Polytechnic Institute, 2003
© E. F. Schubert, Rensselaer Polytechnic Institute, 2003 5 History of the first transistor “The first transistor was about half an inch high. Before Brattain started, John Bardeen told him that they would need two metal contacts within 0.002 inches (0.002 inches = 50 µm) of each other - about the thickness of a sheet of paper. But the finest wires then were almost three times that width and couldn’t provide the kind of precision they needed. Instead of bothering with tiny wires, Brattain attached a single strip of gold foil over the point of a plastic triangle. With a razor blade, he sliced through the gold right at the tip of the triangle. Voila: two gold contacts just a hairwidth apart. The whole triangle was then held over a crystal of germanium on a spring, so that the contacts lightly touched the surface. The germanium itself sat on a metal plate attached to a voltage source. This contraption was the very first semiconductor amplifier, because when a bit of current came through one of the gold contacts, another even stronger current came out the other contact