V()

fn. Dijkstra s name for the semaphore release primitive. V is short for verhogen, which is the Dutch word for increment.

Vcc

(vee see see) n. The power pin to an IC. Mostly used to designate digital power, though rarely one sees this used as an analog device s positive power pin. In digital circuits, this was once always 5 V, today Vcc is edging to lower values to minimize power dissipation in ICs; 3.3-, 2-, and even 1-V power supplies abound.

Vdd

(vee dee dee) n. Positive rail pin for analog and (rarely) some digital ICs. On digital devices most vendors designate power by Vcc; Vdd was primarily used on old-style CMOS chips.

V-F converter

See voltage-controlled oscillator.

vacuum tube

n. A (usually) glass-encased active element used to amplify or rectify a signal. Vacuum tubes (called valves in the U.K.) were, before the transistor, the only active element in electronics (other than selenium diodes and a few other oddities). Like a transistor, the tube is basically an amplifying device. Unlike transistors but similar to FETs it is based on voltage rather than current.

The schematic symbol for a 12AX7.

Tubes have a cathode that emits electrons, one or more grids through which the electrons flow, and a plate to which they are attracted. A small voltage on the grid modulates the current flow. A filament heats the cathode to bake electrons from the cathode s surface.

History: The earliest computers all used vast arrays of vacuum tubes; ENIAC used some 18,000. Because...