Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [high-impedance]

67 questions
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Has anyone measured what a high-impedance pin looks like?

I understand that when an IC pin is in a high-impedance state, the pin is not connected to anything internal. It will be at the voltage to whatever it is being pulled from the outside. I am just curious as to whether anyone has measured the value of…
user220456
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3 answers

Cleaning circuit boards for high impedance

Colleagues, EEG signals typically have high source impedance. Amplifiers in the EEG circuits have high input impedance too. The signal is DC-coupled to the amplifier. One problem is that leakages across the surface of the board can distort the…
Nick Alexeev
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How can I differentiate between high and high-Z state?

I'm using this MCP73831 device. I want to know how what to expect as a voltage level on the STAT pin when the below chart on page 13 says, STAT = HIGH & STAT = HIGH-Z. When the charging is completed, I need to see HIGH voltage (say if Vdd is 5V,…
user220456
5
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6 answers

Difference between no input and a zero input in digital electronics

I'm new to digital electronics and try to understand how logic gates works. In books many times Zeroes​ and ones are referred as Low and High respectively, is Low and High used as an indication of lower input voltage and higher input voltage ? And…
user215805
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How to put a 74HC165 on an SPI bus?

If I want to read a (bunch of) 74HC165 chip(s) over an SPI port on a microcontroller, this is simple enough. Connect them through Q7 to DS on each, apply the final Q7 to MISO, notCE to SS and CP to SCK. This works fine. But now how do I share the…
LeoNerd
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Is there such a thing as a circuit that outputs 1 if the input is high-impedance, and 0 otherwise?

I am trying to design a circuit that outputs a logical 1 if the input is high-impedance, and a 0 otherwise. Any idea how I might implement this? I would prefer to use off-the-shelf parts (no programming). Truth table: I|O --- X|1 0|0 1|0 I was…
Codeman
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Why high impedance source in ADC input causes error?

Recently, I had a problem with two sensors (LDR and LM35), when I tried to read them in Arduino ADC, both measures were totally wrong. Searching in the internet, the answers are related with high impedance of voltage divider provides to analog pin…
Kaorthraya
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What is the resistance of a typical PCB?

What is the typical resistance between two points on a "typical" PCB? Let's say the points are 1mm apart and let's assume a normal office environment. I've noticed that resistors come in many values, but resistors larger than 10 megaohm are rare or…
avl_sweden
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Is there a circuit to detect if a line is high-impedance?

I was wondering if it was at all possible to detect a high-impedance state. I intend to use it with a LS245 within a register. It should essentially be able to turn on an LED (bring the output to HIGH). Here is the schematic I have so far of the…
Aiden K
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Is there a standard way of doing a TTL Hi-Z buffer?

I found many examples of IC internals for CMOS Hi-Z (tristate) buffers, but none for the TTL family. I guess that in the TTL world, the "open collector" is much more common, but I see that there are some three-state 74xx also. The following circuit…
Steve Schnepp
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Removing high impedance ground pours parallel to signal traces in Altium

whenever I route parallel traces on Altium, I get those narrow ground pours between my signal traces when I fill my ground planes. A collegue told me: since these pours are narrow and thus high impedance compared to a ground plane, they would pair…
JCSB
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The "10x rule" for impedance bridging

Quoting the Wikipedia impedance bridging article . . . A connection is commonly said to be bridged if the load impedance is at least ten times the source impedance. Why the magical numer 10? To give this question some context: If designing a…
learnvst
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Shift register Tri-State and ULN2803A

I was planning to use the SN74HC595 shift register in association with the ULN2803A and MIC2981 to switch on and off some loads based on the data of the shift register. What happens if I disable the output of the shift register (using the OE line)…
Fredovsky
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High impedance in RTL Verilog

I am designing a shift register. It has a control signal called RD which is asynchronous (so I can't use it inside the procedural block). The whole point is my n-1 bit shift register is value of the input if RD==1 or else it has high impedance; I am…
Dig_Verif_bee
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How to measure open-drain vs. hi-z with multimeter

I have an output pin configured to be either open-drain or hi-z. How can I use my multimeter to tell which mode it is in?
Hesky Fisher
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