# Tag Info

25

Couldn't it be replaced with a simple resistor into ground like this? Yes it can and is has been done: PMOS logic there's also the complementary version: NMOS logic We've been there and done that! So why are we almost exclusively using CMOS these days? Think about the situation when the PMOS or NMOS (in PMOS or NMOS logic) is switched ON. Then a current ...

4

In the early days of MOS (and, indeed, bipolar logic) they did exactly that: used only one type of transistor and used a pull-up or pull-down resistor built in silicon to achieve the opposite state. This was an economical way to make logic that used fewer process steps, in a time when extra process steps were very expensive (they’re still not cheap, but the ...

3

It sounds as though you think the AND gate might be edge-triggered. It's not. It's purely combinational logic and the timing is irrelevant. A B Z 0 0 0 0 1 0 1 0 0 1 1 1 Table 1. The AND truth table has no timing considerations.

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I think you understand, given your earlier comment! That's fantastic. Plus, you've shown your work. To start, here's the transition table for a JK FF: \begin{array}{c|c} \text{Transition} & \text{JK FF} \\\hline {\begin{smallmatrix}\begin{array}{c} \text{start }\to\text{ end}\\\\ 0 \quad \to \quad 0\\ 1 \quad \to \quad 1\\ 0 \quad \to \quad 1\\ ...

3

A Mosfet always has a voltage drop associated with it. So if you want to switch within the full boundaries (V+ <-> V-) you need both channels. If you are okay with the voltage drop on your output signal (V+ - x) you are good to go. But think about cascading. This effect worsens with the number of sequential arrangements.

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this is the sort of thin that cauld be solves using 12V capable logic and a few resistors. Old-school CMOS logic is good to 15V or more so use CD4001 or HEF4001 - you'll need one chip for every two illuminatred switches. simulate this circuit – Schematic created using CircuitLab

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simulate this circuit – Schematic created using CircuitLab Figure 1. A possible solution. (LEDs are 12 V and have built-in current limiting.) How it works: RLY1 switches between day (blue) and night (red). If the individual switch or button is off Q1 or Q2 is turned on depending on the day/night setting. If SW1 is pressed D7 and 8 conduct pulling the ...

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Every trace has some capaticance C. Resistor from your example will form lowpass filter with cut-off frequency fc=1/2PiR*C. Lower R gives highier cut-off frequency. Lowest R you can achieve with MOSFET. It's just allow you to speed up switching.

2

A typical simple logic gate is continuously operating. It's output follows its input(s) in real time, and there are always inputs. Even if the input pins are unconnected the gate will still try to interpret them as logic values. If one input happens to change before another, the gate will simply continue to do its job and produce whatever output corresponds ...

1

You already got the S output. Tips: Can you make an inverter (one input and one output) using a XOR and connecting one of the inputs to a fixed level? You can make any circuit using NANDs, right? As @user_1818839 said, it doesn't have to be elegant!

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Yes, if you use XOR gates to invert the inputs and outputs of the AND using XOR gates wired as inverters. That’s just one way, there are others, like using cascaded half-adders.

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The complementary pair at the output of a CMOS gate is circuit "C" here: simulate this circuit – Schematic created using CircuitLab As you can see, it might be considered to be a merging of circuits "A" and "B", where we replace resistor R in "A" with the MOSFET from "B", or vice versa., and tie the ...

1

The circuit you showed us here is not a logic gate. It's something that creates light (or not) depending on the positions of switches. In other words, your circuit converts certain combinations of finger actions into some light level. A logic gate takes potentials (voltage levels) as its inputs, and creates a potential as its output. It converts voltages to ...

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