The Schottky TTL gate was the next improvement in the technology. resistor values are lowered to reduce the propagation delay. the resistor values are higher than in the standard gate in order to reduce the power dissipation.
The speed of the gate is inversely proportional to the propagation delay. because lower resistances draw more current from the power supply. the trade-off is higher power dissipation. Reducing resistor values in the circuit reduces the RCtime constants and decreases the propagation delay. Reducing the storage time decreases he propagation delay. The propagation delay of a transistor circuit that goes into saturation depends mostly on two factors: storage time and RC time constants. as then designed with different resistor values to produce gates with lower power dissipation or with higher speed. The standard TIL gate was the first version in theTIL family. because it indicates that a given propagation delay can beachieved without excessive power dissipation. the speed-power product is measured in picojoules (pJ ).A low value for this parameter is desirable. The product of the propagation delay and power dissipation. and propagation delay were defined in Section The speed-power product is an important parameter used in comparing the various TIL series. Commercial TIL ICs have a number designation that starts with 74 and follows with a suffix that identifies the series.
#TOTEM POLE OUTPUT FOR TTL LOGIC FAMILIES SERIES#
The names and characteristics of eight TIL series appear in Table 10.2. There are several subfamilies or series of the TTL technology. are the dominant technologies in VLSI circuits. which will be discussed in Sections 10.7 and 10.8. improvements were added to the point where this logic family became widely used in the design of digital systems. this means that the circuits in this series can be connected to inputs and outputs of TTL ICs without need of additional interfacing circuits.The original basic transistor- transistor logic (TIL) gute was a slight improvement over the DTL gate. The 74HCT series is electrically compatible with TTL ICs. The high speed CMOS 744C series is an improvement of the 74c series with a tenfold increase in switching speed. the performance characteristics of 74c series are same as 4000 series.
The original design of CMOS ICS is recognized from 4000 number designation. in any case, TTL gates in all available series come in 3 different types of output configuration: Open collector output, totem-pole output and three state (Tri-state) output.Ĭomplementary MOS (CMOS) circuits take advantage of the fact that both n-channel and p-channel devices can be fabricated on same substrate.ĬMOS circuits consist of both types of MOS devices interconnected to form logic functions. The differences in TTL series are not in digital logic that they perform, but rather in the internal construction of basic NAND gate. the effect of the schottley transistor is to remove the storage time delay by preventing the transistor from going into saturation.This series increases the speed of operation without an excessive increase in power dissipation. The schoyley TTL gate was the next improvement in the technology. In the low power TTL gate, the resistor values are higher than in the standard gate to reduce the power dissipation, but the propagation delay is increased. The standard TTL gate was the first version in the TTL family, this gate was designed with different resistors values to produce gates with lower power dissipation or with higher speed.
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