In each case, the AC input voltage is stepped down to a value in the 9-12 V range via transformer T1 (which has a VA power rating at least double that of the final power supply’s DC output). These are typical TTL PSU designs, and all work basically the same way. Three power-supply circuits are shown in Figures 1 to 3. The PCB’s supply rails should be liberally sprinkled with 4.7 ♟ tantalum electrolytic capacitors (at least one for every 10 ICs) to enhance low-frequency decoupling, and with 10 nF disk ceramics (at least one for every four ICs, fitted as close as possible between an IC’s supply pins) to enhance high-frequency decoupling. Connections and interconnections should be as short and direct as possible. In general, the TTL circuit’s PCB’s +5 V and 0 V supply rail tracks must be as wide as possible (ideally, the 0 V track should take the form of a ground plane). Consequently, practical TTL circuits should always be powered from a low-impedance, well-regulated supply such as one of those shown in Figures 1 to 3, and must be used with a PCB (printed circuit board) that is very carefully designed to give excellent high-frequency supply decoupling to each TTL IC. The 74-series TTL ICs are designed to be used over a very limited supply voltage range (4.75-5.25 V), and - because they generate very fast pulse edges and have relatively low noise-margin values - must be used with supplies with very low output impedance values (typically less than 0.1 Ω). Assuming that the matter of fan-in and fan-out has already been taken care of (as described in Part 2 of this mini-series), four other basic usage themes remain, and these are described under the headings Power Supplies, Input Signals, Unused Inputs, and Interfacing. Our product offerings include millions of PowerPoint templates, diagrams, animated 3D characters and more.It is usually a fairly simple matter to design logic circuitry using “74-series” TTL ICs, provided that a set of TTL basic usage rules are observed. is brought to you by CrystalGraphics, the award-winning developer and market-leading publisher of rich-media enhancement products for presentations. Then you can share it with your target audience as well as ’s millions of monthly visitors. We’ll convert it to an HTML5 slideshow that includes all the media types you’ve already added: audio, video, music, pictures, animations and transition effects. You might even have a presentation you’d like to share with others. And, best of all, it is completely free and easy to use. Whatever your area of interest, here you’ll be able to find and view presentations you’ll love and possibly download. It has millions of presentations already uploaded and available with 1,000s more being uploaded by its users every day. is a leading presentation sharing website.
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