![]() ![]() If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance. All information these cookies collect is aggregated and therefore anonymous. They help us to know which pages are the most and least popular and see how visitors move around the site. Performance Cookies: These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. If you do not allow these cookies then some or all of these services may not function properly. They may be set by us or by third party providers whose services we have added to our pages. Functional Cookies: These cookies enable the website to provide enhanced functionality and personalization. These cookies do not store any personally identifiable information. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. Strictly Necessary Cookies: (Always Active) These cookies are necessary for the website to function and cannot be switched off in our systems. After we finish updating our website, you will be able to set your cookie preferences. Early microprocessors were implemented using only this trivial circuit.Īnalog Devices is in the process of updating our website. All other logical operators can be implemented using only NAND gates connected in different configurations. The popularity of the NAND gate is derived from the fact that it is the easiest of the digital logical operators to implement using transistor technology, e.g., a two-input NAND gate uses only four transistors when implemented in CMOS. While all windows and doors are closed, the alarm output is “0.” If a single window or door is opened, the security system output changes state to become “1” and this can be used to trigger an alarm or take some other action. If a window/door is closed, the sensor sends a logical “1” signal to the security system. For example, a simple security system consisting only of NAND gates could be used to monitor the status of sensors connected to windows and/or doors. NAND gates help detect if a single input to a digital system has gone low. ![]() Symbol and truth table for NAND gate What are NAND gates used for? The Boolean expression for a NAND gate with two inputs (A, B) and output X is:įigure 1. The symbol and truth table for a NAND gate is shown in Figure 1. While an AND gate outputs a logical “1” only if both inputs are logical “1,” a NAND gate outputs a logical “0” for this same combination of inputs. Chances are that no matter if someone's building a whole CPU or something more special-purpose and limited, that someone will be doing so in terms of already-assembled-and-composable gates rather than transistors directly, if only for the sake of one's own sanity.NAND is an abbreviation for “NOT AND.” A two-input NAND gate is a digital combination logic circuit that performs the logical inverse of an AND gate. Building a whole general-purpose CPU from individual transistors is much easier when those transistors are already arranged on a little board you can plug into your bigger board. "Chips" are just discrete components, whether crafted from a single chunk of silicon or itself built out of discrete components and treated as a single discrete unit. One of the key advantages of a general-purpose CPU is that it's general purpose and can be made to do all sorts of different things, but there are certainly plenty of cases where that ain't necessary and you'd need a fraction of that capability at most. There are multiple ways to skin a cat, though (perhaps literally this would be the post-apocalypse, after all!), and you're right that there are numerous ways to put transistors to use besides building full-blown CPUs. There are examples elsewhere in these comments (linked by myself and others) of CPUs with similar (if not greater) transistor counts soldered together by hand out of TTL chips or even out of individual discrete transistors. ![]()
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