Electrical4U 
What is Shunt Reactor A shunt reactor is an inductive device connected in high-voltage power transmission systems to absorb surplus charging vars and hold the voltage down when the load is light. A fixed-rating reactor stays on the transmission line all the time, or it is switched in and out as the load changes. A … Read more
Voltage and current are the two basic quantities in an electric circuit. Those voltage and current figures alone do not tell you how an electric circuit element uses energy. You also need the electric power that a circuit element can handle. A 60 watt electric lamp of the same type usually gives less light than … Read more
When inductors are connected in series, and mutual inductance can be ignored, the equivalent inductance is the sum of the individual inductances. Series resistance of series-connected resistors uses the same addition rule. For inductors that share flux, add or subtract the mutual inductance between those inductors. The effective inductance of each coil then includes both … Read more
A digital integrated circuits logic family is one production style and circuit style that a vendor publishes as a matched set. Parts in that Logic Families group share the same electrical envelope, so one family of ICs can usually plug together without a translator. The shared spec covers supply voltage range, speed class, power, input … Read more
SSI and MSI chips still ship logic gates, flip flops, counters, multiplexers and demultiplexers. Those parts sit at small-scale and medium-scale integration. TTL and ECL used too much area and power for early MOS-scale LSI. CMOS later became the VLSI family. In the MOS-LSI years the dense options were PMOS, NMOS and bipolar I2L. This … Read more
A Schmitt Gates device is a logic gate whose input uses two trip points instead of one. Ordinary gates switch at a single threshold voltage for both rising and falling edges, somewhere between a valid low and a valid high. A slow or noisy edge that lingers near that one trip point can make the … Read more
A logic gate is a digital circuit whose output follows a Boolean function of its inputs. Earlier pages covered the internals of digital logic gates. This page covers common applications of logic gates that follow from that truth table. OR combines trips. AND acts as an enable or inhibit. XOR and XNOR handle parity. NOT … Read more
TTL means Transistor Transistor Logic, a bipolar digital family built from NPN transistors, PN junction diodes and diffused resistors. The usual gate is a NAND gate. Subfamilies include standard 74, low-power 74L, high-power 74H, Schottky 74S plus later LS, ALS and 74F parts. The sections below cover the inner circuit of the main groups. Standard … Read more
Fan-out in digital electronics is the number of same-family gate inputs that one logic-gate output can drive without leaving the valid logic levels. One output can feed several inputs, but only up to that count.The limit is set by how much current the output can source at a high level and how much current it … Read more
Error detection and correction codes add extra bits so a receiver can see whether a digital word was changed in transit, and in some codes restore the original bits. Analog and digital links both pick up errors; a computer or a comms link needs a definite check because one wrong bit can change a code. … Read more