![totem pole output stage totem pole output stage](https://i.ytimg.com/vi/hIOk032t7GQ/maxresdefault.jpg)
The input stage of the NAND gate is a multi-emitter transistor.
#Totem pole output stage series#
7400 Series TTL 2 input NAND gate circuit showing different blocksįrom the circuit diagram the basic blocks of this simple 7400 series IC can be easily seen. The circuit of a basic 7400 series NAND gate is given below. To achieve the tri-state situation, the internal circuitry is arranged so that both transistors in the totem-pole output can be tuned off at the same time. In order to be able to select this state, an additional "enable" input is required on the chip. It is also possible to disable the output so it has no effect on the line being driven - in this state it is open circuit or floating. It is able to provide the high and low of a normal output. Tri-state: This form of output has three states as the name implies.However the speed of switching is much slower and dependent upon external influences. This has many applications including driving indicator lamps. In this way external loads can be connected between the output, i.e. Open collector: This form of output has a single transistor with its emitter connected to 0V.The advantages of using the totem-pole output are threefold: The diode D1 ensures that Q2 is able to turn off rapidly when required. In this arrangement either Q1 or Q2 conducts dependent upon the complementary logic status of the inputs.
#Totem pole output stage driver#
In this arrangement a driver transistor provides complementary voltages for the two output transistors, Q1 and Q2, which form the totem pole output arrangement. It comprises two transistors and enables very fast switching times to be achieved.
![totem pole output stage totem pole output stage](http://www.next.gr/uploads/tutorials/digital-circuits-tutorial/Diagram-1-9-Totem-Pole-Output.png)
The 7400 series TTL ran from a nominal 5 Volt supply line and as a result of its popularity the 5 V line became standard for logic chips for many years, only changing when power restrictions and smaller feature sizes on chips as a result of higher integration and new processes forced the operating voltage down.Īlthough launched in the mid-1960s the 7400 series became the main standard set of logic widely used in electronic digital circuits. The 7400 logic series of ICs were fabricated using bipolar transistor technology and this gave its name to the logic technology, TTL standing for transistor-transistor logic.
![totem pole output stage totem pole output stage](https://www10.edacafe.com/book/ASIC/CH06/CH06-4.gif)
Summary of 7400 Series TTL Key Parameters Some of the main or highlight features and specifications for the 7400 series logic family are detailed below: They have long been superseded by other 74xx00 logic families, but they have been so successful that the basic concept has remained the same. The 7400 series TTL chips remained in use for many years. However the standard parameters remained the same: logic function ( a 7416 and a 74LS16 had the same function they were pin compatible, etc. The 7400 series logic TTL chips spawned a series of other derivative logic families offering slightly different characteristics: high speed, low power, etc. The 7400 series of TTL logic integrated circuits was introduced in October 1966 and they son became the standard for all logic integrated circuits. IC logic families & technolgies summary chart Numbering schemes 7400 Series TTL Logic IC families & Technologies Includes: 7400 Series TTL The 7400 series TTL logic integrated circuits provided the basis for most of the logic circuits of the time and they are still available today.