36
votes
Accepted
What's the difference between a power rail and a signal line?
Yes, both of them are wires, and provide paths for electrons to flow, so they are the same thing. But you may be missing a subtlety: the purpose of a power rail is to carry power (= energy), and the ...
- 10.4k
8
votes
What's the difference between a power rail and a signal line?
One way to look at it is that a power rail optimises for delivering current (and sometimes high voltage), while a signal optimises for delivering high frequency (since the higher frequencies a wire ...
- 306
7
votes
What's the difference between a power rail and a signal line?
A power supply rail is a DC voltage (think of the terminals of a battery) where the DC voltage remains constant over time or, droops (or rises) very slowly. It carries no important information but can ...
- 418k
7
votes
Accepted
5
votes
Accepted
What issues can floating nodes cause?
With this simple case that I drew below, you can see that a floating node can cause
a) unpredictable output. Gate leakages generally determine the voltage of the floating node in this case and we can ...
- 793
4
votes
Accepted
Logic signals have too high a voltage - Solved
A simple series resistor for source termination would likely work fine. On the other hand, what you see on the scope is what the probe sees, and you migh be probing the signal in a way that the scope ...
- 113k
4
votes
Accepted
Turning on an alarm after counter reaches 99
I added a few blocks to your block diagram to meet your requirements
- 793
4
votes
Accepted
How does a 0 as a binary input work if it is given by off?
...that NOT gate has its own power supply, and it simply checks the input and generates output with its own power? Then is it so with all digital systems, and does the input current then never power ...
- 16k
3
votes
Typical efficiency of logical circuit outputs
If I understood you correctly, you are trying to understand the relationship between output, input and operating (intrinsic) currents of ICs and such, and how they all combine to determine the total ...
- 16k
3
votes
Accepted
What's wrong with this CMOS implementation of XOR?
The VTH for the MOSFETS that you have used is 4V. The source of M3 seems to be at 1.25V. As expected it will not go to 0V because the PMOS cannot pulldown to 0V. M5 transistor is OFF because it's VGS =...
- 793
3
votes
Turning on an alarm after counter reaches 99
The instructions say that the alarm should sound when maximum occupancy is exceeded, not when it reaches maximum. So you would need it to sound when the 100th person is added. If you use a counter IC ...
- 11.8k
2
votes
How to write this boolean expression using only NOR gates?
I know this question is old, but maybe this tip will help students in the future, as it has helped me.
When we're looking to represent a logic expression in terms of only NAND or NOR gates, it's ...
- 21
2
votes
What issues can floating nodes cause?
So what can happen in your circuit does not itself depend on how the floating node can affect the logic state, it really depends on what your circuit does with the logic state it receives, as the ...
- 113k
2
votes
Can the output of a logic gate be split to serve as input for other logic gates?
Having a logic output driving multiple logic input is normal. In ideal logic diagrams, a single logic output could drive an infinite amount of logic inputs, and on many occasions, a clock output will ...
- 113k
2
votes
Is the output current from an SPI the same for any line impedance?
Assuming the input is CMOS type input, no current flows into it in DC state.
Since current going into CMOS input is 0, it will be 0 no matter what impedance transmission line you have between logic ...
- 113k
1
vote
Circuit to convert voltages from 3.3 V and 1.5 V to 3V3 logic levels
Here is an easy way to do this, though not exactly what you are asking for:
simulate this circuit – Schematic created using CircuitLab
You should enable the pull-down in the Raspberry Pi input ...
- 360k
1
vote
Typical efficiency of logical circuit outputs
A typical CMOS type logic input draws virtually no current at all when held static. They do have some leakage current, but that is in the order of one microamp, at worst case usage scenario, so in ...
- 113k
1
vote
Digital Design - Reduction Operator
We can't tell you that without knowing which technology / "parts/components" you have at hand.
If you need to wire this together from bijunction transistors, the answer will look very ...
- 84.7k
1
vote
How does a 0 as a binary input work if it is given by off?
Or is it that a NOT gate has its own power supply, and it simply checks the input and generates output with its own power? Then is it so with all digital systems, and does the input current then never ...
1
vote
Protecting MCU digital input with 300m wires
If you are expecting a direct lightning strike, then there's nothing you can do, without some serious hardware.
If the lightning you are talking of is a local strike, you can get a lot of current ...
- 16k
1
vote
In an ALU, is every function calculated simultaneously?
Waste of MUX to combine separate logic gates. MUX is the ultimate any gate. 4way pass-through such as 74CBT3253 make chain comparisons without ripple. From magnitude test we can instantly solve all ...
- 11
Only top scored, non community-wiki answers of a minimum length are eligible