Sud

's profile
image

Biography has not been added


Sud

's contributions
  • 02.12.2017
  • Inverted mode switches
  • Of course you are right. We defined the Vec(sat) as composed as the sum of something we called the "intrinsic Offset" and Ic*Re. The intrinsic offset, I seem to remember, was on the order of 5 to 15 mv. Can't find any of the old datasheets that were produced which specified the part for D-A ladder switch aplication. These parts were very expensive because we had to spec these things very tightly, but in those days we had all the money in the world. (Cost plus fixed fee .. CPFF .. contracts. )
  • 02.10.2012
  • How will you celebrate National Engineers Week?
  • I agree. We are born that way. Just have to figure thingsout and build things. I did the same thing at about 10. CK722.....I still have a couple in my collection of things. Played with vacuum tubes and remember something called a condenser. Boy, how times have changed.
  • 02.12.2017
  • Inverted mode switches
  • The reduced offset voltage can can be explained using old fashioned "T" parameters. The ON offset voltage is caused by base current flowing through Re. However, Rc is much lower than Re, hence less offset voltage if the emitter and collector are exchanged.
  • 02.12.2017
  • Inverted mode switches
  • This is a blast from the past. My first job after college in 1964 was to design an airborne R2R 12 bit A-D ladder. We used inverted transistors for the ladder switches. We drove the basses very hard, effective beta of one or two! It turns out that though the offset voltage is very low, the on resistance is quite a bit higher than in the normal mode. The higher beta drive reduced the on resistance a little. We were able to buy, at a substantial premium, transistors with matched on resistances. At the time there was a transistor called a SPAT (silicon precision alloy transistor) that had matched collector base and emitter base break down voltages. In fact, inverted was the primary market for them, and they were not cheap. ..... Ah yes, the good old days.