• Digital logic gate circuits are manufactured as integrated circuits: all the constituent transistors and resistors built on a single piece of semiconductor material. The engineer, technician, or hobbyist using small numbers of gates will likely find what he or she…

  • Logic gate circuits are designed to input and output only two types of signals: “high” (1) and “low” (0), as represented by a variable voltage: full power supply voltage for a “high” state and zero voltage for a “low” state.…

  • NAND and NOR gates possess a special property: they are universal. That is, given enough gates, either type of gate is able to mimic the operation of any other gate type. For example, it is possible to build a circuit…

  • It is sometimes desirable to have a logic gate that provides both inverted and non-inverted outputs. For example, a single-input gate that is both a buffer and an inverter, with a separate output terminal for each function. Or, a two-input…

  • Up until this point, our analysis of transistor logic circuits has been limited to the TTL design paradigm, whereby bipolar transistors are used, and the general strategy of floating inputs being equivalent to “high” (connected to Vcc) inputs—and correspondingly, the…

  • Let’s examine the following TTL circuit and analyze its operation: Transistors Q1 and Q2 are both arranged in the same manner that we’ve seen for transistor Q1 in all the other TTL circuits. Rather than functioning as amplifiers, Q1 and…

  • Suppose we altered our basic open-collector inverter circuit, adding a second input terminal just like the first: This schematic illustrates a real circuit, but it isn’t called a “two-input inverter.” Through analysis, we will discover what this Circuit’s logic function…

  • The Use of Logic Gate Inverters and buffers exhaust the possibilities for single-input gate circuits. What more can be done with a single logic signal but to buffer it or invert it? To explore more logic gate possibilities, we must…

  • If we were to connect two inverter gates together so that the output of one fed into the input of another, the two inversion functions would “cancel” each other out so that there would be no inversion from input to…

  • The single-transistor inverter circuit illustrated earlier is actually too crude to be of practical use as a gate. Real inverter circuits contain more than one transistor to maximize voltage gain (so as to ensure that the final output transistor is…

  • While the binary numeration system is an interesting mathematical abstraction, we haven’t yet seen its practical application to electronics. This chapter is devoted to just that: practically applying the concept of binary bits to circuits. What makes binary numeration so…

  • The singular reason for learning and using the binary numeration system in electronics is to understand how to design, build, and troubleshoot circuits that represent and process numerical quantities in digital form. Since the bivalent (two-valued) system of binary bit…

  • One caveat with signed binary numbers is that of overflow, where the answer to an addition or subtraction problem exceeds the magnitude which can be represented with the alloted number of bits. Remember that the place of the sign bit…

  • We can subtract one binary number from another by using the standard techniques adapted for decimal numbers (subtraction of each bit pair, right to left, “borrowing” as needed from bits to the left). However, if we can leverage the already…

  • With addition being easily accomplished, we can perform the operation of subtraction with the same technique simply by making one of the numbers negative. For example, the subtraction problem of 7 – 5 is essentially the same as the addition…

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