Questions tagged [high-impedance]

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46 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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3answers
87 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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0answers
275 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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2answers
123 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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1answer
416 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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2answers
52 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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1answer
418 views

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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1answer
93 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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0answers
139 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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1answer
168 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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3answers
916 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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1answer
308 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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2answers
656 views

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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2answers
615 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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3answers
2k 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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1answer
316 views

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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1answer
83 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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1answer
178 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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2answers
305 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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1answer
105 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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1answer
153 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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1answer
2k 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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2answers
3k 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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1answer
183 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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1answer
1k views

tri-state / high-z / high impedance output with gpio input

The Li-ion charger I'm using (MCP73831/2) has a tri-state status output. The datasheet says that the STAT pin outputs High-Z when inactive or complete, and Low while charging is active. Whats the ...
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1answer
296 views

Can logic analyser show high impedance state?

Quick question: are there logic analysers that can show us high impedance state in circuit? I could only find information about different voltage levels for TTL and CMOS, but couldn't find clean ...
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2answers
539 views

Multiplexing buttons using shift register - high impedance output

I have experience with 74HC4094, and I believe the 74HC595 is essentially the same - the datasheet says they have "tristate output", but that is only when OE is low - then all pins are tristate. What ...
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4answers
4k views

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 ...
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1answer
965 views

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?
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1answer
347 views

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 ...
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1answer
135 views

How high is “high impedance” on this chip (CD74HC125E)

I'm trying to interface my electronics with an existing remote. The remote requires me to set one of its pins to either low or nothing (not connected) to activate it. While getting the "low" value ...
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2answers
2k views

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? ...
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2answers
3k views

How can I interface with these 24 V signals?

I have a few 24V inputs to my micro controller from Limit switches. I have conditioned the signals as shown. Pulled down, de-bounced and level converted. I have some signals that are again 24V but ...
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3answers
1k views

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 ...