Programming instructions

 National Instruments Corporation 6-1 Multisim Component Reference Guide
Chapter 6
TTL
6.1 Standard TTL
The characteristics of the standard TTL series can be illustrated by the 7400 quad NAND gate
IC.
The 74 series uses a nominal supply voltage (V
OC
) of 5V and can operate reliably over the
range 4.75 to 5.25 V. The voltages applied to any input of a standard 74 series IC must never
exceed +5.5 V. The maximum negative voltage that can be applied to a TTL input is -0.5 V.
The 74 series IC is designed to operate in ambient temperatures ranging from 0 to 70
° C. The
guaranteed worst-case DC noise margins for the 74 series are 400 mV.
A standard TTL NAND gate requires an average power of 10 mV.
A standard TTL output can typically drive 10 standard TTL inputs.
6.2 Schottky TTL
The basic circuitry of the standard TTL series forms the central part of several other TTL
series, including the Schottky TTL, 74S series.
The Schottky TTL (the 74S series) reduces the storage-time delay by not allowing the
transistor to go as deeply into saturation. The 74S series does this by using a Schottky barrier
diode connected between the base and the collector of each transistor.
Circuits in the 74S series also use smaller resistor values to help improve switching times.
This increases the circuit average power dissipation to about 20 mW. These circuits also use a
Darlington pair to provide a shorter output rise time when switching from ON to OFF.
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