Direct-coupled FET Logic
Direct coupled or Direct-coupled may refer to: * Direct-coupled amplifier * Direct-coupled transistor logic * Direct coupled (applied to an engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...

Direct-coupled Amplifier
A direct-coupled amplifier or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. This is an application of the more general direct coupling. It was invented by Harold J Paz and Francis P. Keiper Jr. in 1955. It displaced the triode vacuum tube amplifier designed by Lee de Forest. Almost all vacuum tube circuit designs are now replaced with direct coupled transistor circuit design. It is the first transistor amplifier design that did not include coupling capacitors. The direct-coupled amplifier allowed analog circuits to be built smaller with the elimination of coupling capacitors and removed the lower frequency limitation that is dependent on capacitors. History Paz first started his career at Bell Labs as an intern from December 1950 to April 1952 as an Engineering Aid. Paz worked o ...
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Direct-coupled Transistor Logic
Direct-coupled transistor logic (DCTL) is similar to resistor–transistor logic (RTL) but the input transistor bases are connected directly to the collector outputs without any base resistors. Consequently, DCTL gates have fewer components, are more economical, and are simpler to fabricate onto integrated circuits than RTL gates. Unfortunately, DCTL has much smaller signal levels, has more susceptibility to ground noise, and requires matched transistor characteristics. The transistors are also heavily overdriven; that is a good feature in that it reduces the saturation voltage of the output transistors, but it also slows the circuit down due to a high stored charge in the base. Gate fan-out is limited due to "current hogging": if the transistor base-emitter voltages () are not well matched, then the base-emitter junction of one transistor may conduct most of the input drive current at such a low base-emitter voltage that other input transistors fail to turn on. DCTL is close ...
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