![]() ![]() Chan School of Public Health, surveyed more than 1,000 parents nationwide about their child care experiences, a third reported difficulty finding care. When NPR, along with the Robert Wood Johnson Foundation and the Harvard T.H. To see a complete list of my articles, please visit this page.One of the most stressful questions a new parent confronts is, "Who's going to take care of my baby when I go back to work?"įiguring out the answer to that question is often not easy. Thus, ECL is particularly advantageous in clock-distribution circuits and other high-frequency applications. Later, PECL became popular because its logic levels are more compatible with those of other logic families such as TTL.ĮCL dissipates a relatively large amount of static power, but its overall current consumption is lower than that of CMOS at high frequencies. ![]() Noise immunity was the main reason for using a negative supply voltage with the early ECL gates. It achieves its high-speed operation by employing a relatively small voltage swing and preventing the transistors from entering the saturation region.Īn ECL implementation that uses a positive supply voltage is referred to as positive-referenced ECL or PECL. SummaryĮCL is considered to be a very high-speed logic family. This can prevent the power-supply disturbances generated by the emitter followers from contaminating the ECL differential pair. Thus, in some cases it is advisable to use two separate power supply lines: one for the input stage and one for the emitter followers. This is why ECL is an attractive solution for high-frequency clock distribution.Īs a final note, the emitter followers (see Figure 1) must provide large output currents to charge load capacitances, and consequently they can cause significant transient deviations in the supply voltage. ![]() Image courtesy of ON Semiconductor.īelow 20 MHz, ECL draws more supply current than CMOS, but as we go beyond this frequency, ECL becomes more efficient. However, if we consider dynamic power consumption, ECL can be more efficient than CMOS, especially as the frequency of operation increases. If we focus on static power consumption, ECL is a high-power logic family. To get familiar with this logic, let’s examine an ECL inverter/buffer as shown in Figure 1. ![]() Emitter-Coupled LogicĮmitter-coupled logic is a high-speed bipolar logic family. This article will review the operation of a basic ECL inverter/buffer, and then we’ll look at some of the most important features of this logic family. In the late 1960s, when the standard TTL family offered 20 ns gate delay and the CMOS 4000 family had delays of 100 ns or more, ECL offered an incredible delay of only 1 ns! ECL achieves its high-speed operation by employing a relatively small voltage swing and preventing the transistors from entering the saturation region. This article will review the operation of a basic ECL inverter/buffer, and then we’ll look at some of the most important features of this logic family.Įmitter-coupled logic (ECL) is a BJT-based logic family which is generally considered as the fastest logic available. ![]()
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