Questions tagged [high-impedance]

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Why is the voltage across high impedance indeterminate?

The analog pins on my Arduino read sporadic values when unconnected, and my multimeter (set to VDC) shows random values when there's no connection between the probes. If I connect the analog pins on ...
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329 views

How does an Instrumentation Amplifier reduce DC offset?

While researching different current measurement methods, I came across a particularly interesting circuit which has a very high input impedance and apparently reduces the effects of the input offset ...
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STM32G0 Seems to output 0.77 V on the input pin when set to high impedance and nothing else is connected to it, why does this happen?

Currently I have an a pin on an STM32 set to be an input and floating (high impedance). When the device it was measuring from was powered down and nothing was going on I was measure about 0.35 V on ...
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High impedance voltage source measurement with ADC

I would like to measure voltage coming from a photodiode in open-circuit condition. The measurement is OK with classical digital voltmeter, but with an ADC internal (SAR) or external (Delta-Sigma) on ...
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5 votes
6 answers
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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 ...
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Voltage divider high resistace

I need to build voltage divider to measure the battery voltage (7.3V) using max 3.3V ADC. As the device most of the time spends in the sleep mode (<1uA), the current drawn from the battery should ...
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2 answers
42 views

Smallest Footprint Source Only (No Sink) Buffer Solution [closed]

I'm currently in the process of designing a cable snake cable tester for recording studios that involves testing for connectivity between a large number of inputs. This involves using a ...
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1 vote
1 answer
71 views

Why an does an offset on the reference electrode create an offset on the measure electrode of a pH probe?

I am making an analog front end for a pH probe. I encountered a design where creating an offset on the reference electrode creates an offset on the measure electrode. How does that work? Does the ...
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3 votes
1 answer
80 views

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 ...
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2 answers
332 views

CAN Stub node termination in a network - 9.28k resistor

In a CAN network, the ends of the network has to be terminated with 120 ohm - I understand this. The middle node in the below diagram is the stub node and it does not have to be terminated, my stub ...
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3 answers
288 views

Circuit that can switch between Vcc and High-Z

I want to develop a switching circuit (for controlling power, rather than digitial signals) that is able to take an input and switch between Vcc and high impedance, rather than switching between Vcc ...
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1 answer
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Multiple differential tranceivers on single bus

Im using a few moduls of rs422 tranceivers connected on single bus Easy module has transciver with TX input, RX output power end differential pair output and input - but no EN pin to hold the ...
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4 answers
823 views

How is high impedance state physically different from a logic low state?

I have read this question and the answers that follow on the electrical stack exchange but I still face a difficulty in understanding the practical difference between high-Z state and 0 state. It is ...
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3 answers
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Microcontroller Unused pins Configuration

I am having this microcontroller - S32K142 64 pin 5V core voltage I have a few pins which I don't want to use. While checking the datasheet of the Microcontroller, I couldn't find any information ...
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Effect of high impedance Opamp buffer on current lost

In the below figure, end-user have the choice to output 4-20mA or 0-10V (using MUX control by uC), I have inserted high impedance buffer(The part number is not correct) with the voltage divider to ...
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1 answer
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disagreement between theoretical calculation and measurement of upper cutoff frequency of a circuit based on RG58 coaxial cable

For a 100 meters RG58 coaxial cable, according to the datasheet, the capacitance of the cable is 10 nF and the inductance is of 25 µH approximately. A sinusoidal voltage is applied at the input of the ...
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26 views

Measure high impedance with low internal impedance device

I was given this thought by one of my co-workers (we're both still novices when it comes to electronics). Background: we have a device with a small internal impedance and have to measure a high ...
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2 votes
3 answers
2k views

When is a wire considered high-Z?

I need to make sure I understand perfectly the high-Z state and its relation to voltage.I intend to explain what I have understood based on three example, is there something wrong ? Let's consider ...
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1 vote
1 answer
185 views

Calculate Voltage Seen at High Impedance Pin

Background I am designing a simple lamp dimmer circuit for use with a 450W bulb for the purpose of heat fusing various synthetic materials. I have the basic dimming functional but now I am ...
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1 vote
1 answer
142 views

Buffer / Line driver ; 3 state IC Working

I am just curious to understanding the working of this - Buffer IC (Part Number - 74AHC1G126) My questions : I figured out that this IC does not act as a level translator which changes the voltages ...
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2 answers
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How does TXS0108E keep it's outputs at high impedance given it's internal block diagram?

I am trying to understand the block diagram of the TXS0108E bidirectional logic shifter. In the chip's description it says When the output-enable (OE) input is low, all outputs are placed in ...
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4 answers
961 views

Buffers output load in unpowered state

Lets take under consideration a 3 state buffer, such as this one: Since the datasheet doesnt provide the information about the internal build of the buffer, I was wondering either it is safe to ...
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1 answer
1k views

Basic of a charged piezo : pC/G, mV/G, Signal analysis

This is the first time I use a High impedance piezo sensor and the problems went pretty quickly. Here is the piezo I used : Manufacturer part number : PKGS-00GXP1-R Rating : 0.35pC/G (+/- 15%) ...
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1 vote
2 answers
289 views

Tri State/Floating Signal Detection

I'm working on a project for automotive environment in which I need to read signals from the power mirrors switch in a microcontroller. The power mirrors switch controls the mirror's moving directions ...
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1 answer
259 views

Connecting logic gate input pin with pull up resistor to another driver input pin doesn't keep the voltage

I have a circuit with logic gates that implements a function in order to get 3 logic control signals. This logic works with 12V or 0V for high and low states. Logic input pins will be connected to ...
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1 answer
148 views

Turning a high impedance output state to a concrete voltage value using a pull up resistor

I have this switch datasheet. I also have a connector with default pins arriving to switch D point. S points are connected to another circuit point. Note: D side connector is an output connector ...
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2 answers
177 views

Inverted high impedance / pull down circuit

I'm devising a circuit to control the shutdown input on an integrated circuit. The IC accepts a high impedance input (can't be pulled to any voltage) to enable operation, or it can be pulled down to ...
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3 answers
337 views

Driving a high-impedance load from a BJT base

Are there any caveats with tapping off the base of a BJT to drive a high-impedance load, such as a logic gate or op-amp? In the schematic below, I have an open-collector output from ...
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1 vote
0 answers
335 views

high input impedance circuits

Working with circuits to get high input impedance. This is to capture signals while introducing as little interference as possible to the preexisting circuit, to load the source as little as possible. ...
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3 votes
2 answers
267 views

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 ...
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1 answer
1k views

How to design a high impedance buffer circuit?

How can I design a buffer circuit that takes an input of +/- 10V and scales it down to a 0V to 5V. The idea is to design a circuit that is microcontroller compatible (can be read by an analog-in pin ...
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2 answers
63 views

Connecting Difference Amplifier to High Impedence Sensor

I have a high impedance differential sensor (stable 600k impedance Rth, 10mV signal, Fout=1kHz). I need to amplify this signal to about 1V (40dB gain). Due to layout/system constraints only the ...
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-1 votes
1 answer
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getting outputs in simulation as all high impedance. topic: restoring algorithm for binary division

I am getting outputs of my hardware as all high impedance (ZZZZZ). i tried synthesizing the code and got these warnings. I think there might be a problem in the test bench i am trying to run. ...
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-1 votes
1 answer
230 views

What would be logic value of high impedance TTL output connected to LED

Suppose a TTL output in high impedance is connected to a LED, which is also connected to a resistor, which is then connected to ground. No circuit interferes between TTL output and LED, between LED ...
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1 vote
0 answers
221 views

OPT301 Photodiode Output Measurement

I am working on a setup where OPT301 is fed with an optically filtered light output yield a very low current which is then Current to Voltage converted by integrated op-amp within the device, but the ...
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1 vote
1 answer
701 views

History of choice of 'Z' to represent high impedance?

I'm curious to know why 'Z' was chosen to represent high impedance state for types such as used in VHDL and VHDL-AMS's std_logic_1164 logic system: (image of page 789 of The System Designer's Guide ...
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4 votes
3 answers
3k views

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 ...
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0 votes
1 answer
520 views

Inverter : drive with high impedance. Results on the output

I have to compile a 9-valued logic table for a circuit. I would like to know what happen to the output of an inverter and of a pass-transistor-gate if driven in high impedance. Specifically in this ...
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2 answers
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Strange Voltage Levels in a Multi-slave Full-duplex rs485 bus

I am working on a project using rs485 bus for communication. Here are design parameters: Bus can include 1 master and 30 slaves Configuration is full duplex using 4 wires. All slaves attached to <...
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0 votes
2 answers
1k views

Is high impedance important for a differential amp measuring a battery voltage?

I want to measure voltages of multiple cells which are connected in series. I want to do that using a differential amplifier. I read about low input impedance, and what to do about it in this case. So ...
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3 answers
3k views

What is the impedance of a Microchip PIC I/O Port configured as input when Vpin > Vdd?

I'm using a PIC18F1320, and it is powered with VDD=4V. There is an external power signal, with a higher value than VDD. The external signal is connected to the RB5 I/O port through a voltage divider: ...
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High impedance op-amp using guard ring to drive a shield

http://imgur.com/a/GSALb http://imgur.com/gallery/9QrWO So I'm looking at the first picture and I'm trying to figure out now the whole shielding part of the circuit works right now. The second image ...
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-1 votes
1 answer
163 views

Measuring a capacitively-coupled potentiometer

Note: this is in problem/solution format, in terms of what I have already thought of. I know I know little enough to be prone to XY problems, and as such if there's a subproblem / subsolution that ...
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1 answer
351 views

Do high impedance pins have input capacitance?

I come from a software background and I'm trying to implement a simple counting circuit. I am using this SN74LV8154 binary counter in a circuit which allows the outputs to be set to high impedance. ...
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2 votes
2 answers
619 views

How to reduce a pulse voltage maintaining a high impedance?

I have one pulse with 200ns and 60 V. I have to reduce this voltage until 10 V min because of the monostable multivibrator. After this, I will extend the pulse with a monostable multivibrator and then ...
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0 votes
1 answer
231 views

Open collector to high-z

Keeping it completely analog, is there a way to high-z an open collector output? An open collector always allows a path to or from a specific voltage potential and this is complicating a rather simple ...
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0 votes
1 answer
231 views

what kind of circuit structure can I use to obtain high output impedance?

what kind of circuit structure can I use to obtain high output impedance? In my design I need an amplifier whose output impedance is extremely high,which structure can do this? I read in Sansen's ...
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-1 votes
1 answer
3k views

My output in verilog is high impedance all the time. Why is that?

I am new to verilog and I have been writing code for 4 bit adder/substractor in structural model. My values of x0,x1,x2,x3,c1,c2,c3,cb and ...
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4 votes
2 answers
5k views

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, ...
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0 votes
1 answer
202 views

Complementary Transmission Gate Circuit

Here is the circuit. Now what would be the voltages at Node Y on the positive edge of the clock, if Switching Time from on to off and off to on of Transmission Gates are : 0.5ns, 1ns, 2ns
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