Questions tagged [voltage-reference]

Anything related to the design and implementation of voltage references, i.e. circuits behaving like fixed (constant-value) voltage sources whose output voltage can be deemed very precise, accurate and stable. Voltage references are not meant to provide significant current to external circuits.

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Do I need a precise voltage reference for my ADC if the what I am measuring shares the ADC voltage source?

I'm trying to design a basic measurement system using some phototransistors and ADCs to measure light absorption via a voltage drop. I've attached a schematic for a quick and dirty representation of ...
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3 votes
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94 views

How to measure voltage with a floating supply?

In the example below, ground of a dual supply is referenced to +Vout. Assuming we have a MCU connected to VCC and +Vout, if we then try to measure the voltage at +Vout with the ADC, we're basically ...
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Offset amplifier's input to prevent opamp clipping

We can do this: With AC coupling and biasing op-amp input. Summing using buffered resistor Using sum and difference inherited in OpAmp and sum signal with desirably created virtual ground 1 is good ...
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Unity gain non-inverting op-amp do not have reference signal, why?

As you know, asimple amplifier with input to its + and out shorted to - its output will follow its input almost exactly. Where is it's input reference input? How I can connect it to the desired ...
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3 votes
1 answer
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VSSA/VSS and Vref - ADC

For measuring a voltage via an ADC into a microcontroller (STM32), is it better to set the reference voltage (Vref) referenced to VSS or to VSSA ? The voltage that I want to measure is referenced to ...
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Can I drive a bridge sensing circuit with a voltage reference?

On the specification sheet there is this application circuit where the sensing bridge circuit is driven by the same voltage reference IC that sets the voltage reference (REFP) of the ADC. I remembered ...
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Mux Auto Addressing Circuit

I am trying to build a circuit that will allow multiple (up to 4) muxes on the same I2C line. I am trying to get their addresses to increment with each new board connected. (Lines A0 to A2). Here is ...
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2 answers
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Using a reference voltage in place of GND for ICs

Problem as follows: I have a reference voltage that must not be loaded and a separate load that must be driven at a minimum of the reference voltage, but must be adjustable from the reference point to ...
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Should ADC reference pin also be a kelvin connection?

Reasking this question with a proper schematic: I am doing a ratiometric measurement of a Thermistor. The thermistor is located over 5 metres away from the ADC and all other components. This is going ...
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4 votes
3 answers
262 views

Is there an alternative economical low-voltage reference to a single cell?

This is a simple Li-ion battery monitor circuit I designed around a low-voltage LMV331 comparator, which can operate down to about 2.7 V. I think it's best for a comparator to work with median ...
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1 vote
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PWM output for DAC and using DAC as reference voltage

I would like to use a DAC as a programmable reference voltage for a window comparator. The input of the DAC would be the Arduino's PWM output. Can I connect the Arduino's PWM output directly to the ...
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How to keep the reference voltage constant for comparator?

I want to build a circuit with a comparator, but the reference voltage is changing (CH3-purple) as seen in the oscilloscope image. I used the TL431 as in the image to keep the reference voltage ...
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How do I determine what range (not necessarily value) of resistors to use for voltage dividing [duplicate]

I'm getting back into electronics as a hobby and doing some refreshers having been away from it for a long time. I understand Ohm's law and voltage dividing, however, I'm not sure I understand what ...
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3 answers
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Is there any use of a 65 mV reference voltage?

I am a senior studying electronics, and have happened to make a bandgap reference circuit that gives out an output reference voltage of ~65 mV. I've constructed this after quite a few months of ...
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1 vote
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Voltage reference to drive multiple thermistors - high precision with op amp to supply current, or just generic voltage ref?

I would like to drive 8 thermistors in parallel. They will be driven from 2.5V in a voltage divider. This will be about 20mA current draw. I will be using a ratiometric measurement where the ADC ...
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Is the LM399 Temperature coefficient with the heater on or off?

The LM399 datasheet specifies a temperature coefficient "\$\Delta\$T/\$\Delta\$Temp". The conditions state an ambient range but don't specify if that's with or without the heater on. Which ...
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1 answer
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Why does my output get supercompensated?

I have almost finished a project that was supposed to output a square wave signal with a certain frequency but when I tried to make a small change to the circuit something weird happened to my output. ...
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0 votes
1 answer
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Can't understand how the Zener voltage reference works

I've built a small amplifier circuit in which I've wanted to use a Zener diode as a reference but I can't figure out how it works. Knowing that the negative rail is -5V and the Zener breakdown ...
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2 answers
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LM4040 Shunt Voltage Reference Functional Diagram Explanation

Could you help me understand how this shunt voltage reference circuit operates? Cathode connects to Vin while Anode typically connects to ground (unless floating). This circuit is from the LM4040 ...
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12 votes
3 answers
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Need help understanding schematics in LT1019 datasheet

We are currently using AD7795 to get ratiometric reading of 4 load cells. It works, but the chip stocks are rather volatile. So, I am thinking on using much cheaper and easier to come by MCP3424/...
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1 vote
1 answer
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Standard approach for a split power supply ADC?

I'm currently working on a project that will incorporate an AD7124-8 ADC, which as far as I understand can accept true bipolar inputs when provided a split supply. I tried to dig around for an app ...
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Measure ATmega168PA internal temperature while using other ADC channels at 5V reference

I have a device that continuously measures the value of 3 sensors connected to 3 ADC pins and working at 5V reference, so I have two options for voltage reference selection: Connecting AREF pin to 5V ...
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Powering an op amp from a Reference voltage?

Let's say I had a low power op amp (pre-amp stage) going to an ADC (LTC2412). My question is: If I wanted a super precise, low noise, low TC drift, positive supply line could I just power the +A5V ...
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2 votes
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How do I use a Zener diode (LM4040) shunt voltage reference?

I would like to place a voltage reference for my MCU ADC. This is my first time using voltage references. I have chosen is the LM4040. It is relatively cheap and pretty good. I am getting the 3V 0.2% ...
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Reference input current value for TL1431CL5T voltage reference

There appear to be some mismatch for Iref value between the table and the graph for part TL1431CL5T. In the table it specifies the maximum value as 3uA where as in the graph it specifies as 1.7uA at -...
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Minimum voltage reference for ADC

I am looking to measure very low voltage signal (0-0.5V range) and was wondering if it is possible without amplification. I am a bit confused about what the minimum references of ADC can be. Looking ...
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1 answer
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Dificulty deriving voltage reference ripple

I have this voltage reference circuit and I need to derive the equation that gives me the influence of \$\Delta\$Vio on the output Vref which is my Vo, I have derived the equation for Vo when \$\Delta\...
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0 votes
4 answers
196 views

Precise multi-point over-temperature control using comparator

This circuit will (hopefully) send a signal to MCU if over-temperature is observed in any of the NTCs. Using LM339 as comparator, and a reference voltage (from TL431), assuming high precision for NTC ...
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7 votes
2 answers
683 views

Buried zener voltage reference: noise vs temperature

Buried Zener voltage references like LTZ1000A are known for their low-noise. High stability of reference voltage is often improved by temperature stabilization at somewhat elevated temperature. I ...
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1 vote
1 answer
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Voltage drop by reference voltage generated by zener diode

I am now designing a circuit looks like this: simulate this circuit – Schematic created using CircuitLab My goal with this circuit is to compare the input digital signal with a reference signal ...
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0 votes
2 answers
49 views

AD7190 noise performance calculation

I'm using ad7190 to sample single-ended voltage. The rms input-refered noise is given by the datasheet. However, the datasheet only specified the noise with 5V reference, whereas I'm using 4.096V ...
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1 vote
1 answer
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Reduce 2.503V regulated voltage by just about 3mV

I have a handful of REF192GP reference voltage sources. They are specified to produce a relatively precise 2.5V. Measuring each device I typically get a few mV higher than 2.5V, for example 2.503V. ...
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1 answer
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Ground Reference for multi layer board

I am currently designing a multi-layered PC board and there is situation where signals are referencing the ground plane meant to be used for the 3.3v supply. So, for example. I have a 3.3v plane on L8 ...
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1 vote
2 answers
85 views

Voltage reference output impedance calculation

I'm using AD7190 to sample 4ch single-ended signal. The datasheet suggests ADR431 or ADR421 as voltage reference for AD7190. However, an article on Analog Dialogue gives a way to calculate whether an ...
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2 votes
1 answer
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How to feed reference voltage for two op amps inputs with different input signal each one

Im building a Stereo Buffer and a Baxandall circuit together. In powering the circuit with a single supply of 9v, and i need to bias each four inputs with 4.5 volts. The question is: If i feed the ...
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1 vote
1 answer
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Beginner Question: Get 2 Reference Voltages for Comparator using Voltage Regulators

I'm working on a project where I have a 12 V voltage supply. I need reference voltages of 4.5 V and 3 V which will be each be used as the Vref for a comparator. I am aware that I shouldn't use a ...
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0 votes
0 answers
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Fixed voltage drop (current and temperature independent)

simulate this circuit – Schematic created using CircuitLab Is there a clever way to create a fixed voltage drop say 2V that is not affected by current or temperature? Voltage stability should ...
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2 votes
1 answer
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Precision reference voltage: buffering with OpAmp and BJT

I'm designing a reference voltage generator for the analog section of a circuit. Two voltages as needed: Vref = 3 V for ADC Vref/2 = 1.5 V for signal conditioning circuits (with a load of about 40mA) ...
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0 votes
1 answer
108 views

Level shifting with a voltage reference of 1.6V

I am trying to build a level shifting circuit for my project in order to make sure that the input will be appropriate for a 0-3.3V ADC. I am using two 9V batteries connected in series so my thought is ...
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0 votes
1 answer
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Does reference voltage long term drift reset after a power cycle?

I'm building a 16-bit ADC system to measure the analog output of an ASIC and accuracy is of utmost importance. One subcomponent required for any ADC system is the reference voltage. When choosing a ...
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1 vote
2 answers
73 views

How does this voltage-reference circuit works [duplicate]

I have been trying to understand how this circuit works for the past few hours, it is supposed to be a voltage reference circuit that uses a zener diode, I am supposed to derive an expression for Vout ...
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0 votes
0 answers
54 views

KA336 replacement parts

Can you replace a KA336 with a TL431 directly? I have a circuit board with a broken KA336 and I can't find it here in my country, not even the LM336. It is a 2.5V shunt regulator. The adjust pin on ...
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0 votes
1 answer
203 views

TL431 - negative and positive references point

I am a musician who likes to play around with electronics. For some synthesizer circuits I am working on I need to create two references points using the TL431 - one for negative 2.5V and the other ...
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1 answer
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Digitally variable zener diode reference

I'm trying to use a digital signal (3.3V or 0V) to set a voltage reference for a comparator (4.7V and 6V.) I've come up with the circuit below but it doesn't seem to be very precise and I can't seem ...
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1.6v voltage reference with an input of 9 volt

I am trying to find a voltage reference with an input of 9 volts. I was able to find two from maxim integrated but had a max input of 5v. I was trying to find a fixed 1.6 output but I wasn't able to ...
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0 votes
1 answer
206 views

Virtual ground vs voltage reference

I want to know what is different between voltage reference and virtual ground and can you use both of it as rail-splitter in transimpedance amplifier, if not why. All I know is Virtual ground chips ...
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Improve range on a differential ADC

I'm using an MCP3425 ADC, it has differential inputs but I'm using it as single ended mode. The signal that I want to digitize comes from an integrator circuit (an op amp with a capacitor in its ...
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2 votes
1 answer
138 views

Level Shifting Circuit to output 0.2V-4.8V

Having a sensor's dynamic range from 4V - 10V, I am looking for a level shifting circuit using op-amp that gives me an output of 0.2V - 4.8V. I have been looking through many design yet I could not ...
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5 votes
1 answer
742 views

Bypass cap on reference voltage?

For a voltage reference providing a reference to multiple devices, ADC, DAC, instrumentation amp... would there be some benefit in placing bypass caps right at the reference input to these devices ...
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1 vote
1 answer
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How to modify TL431 current limiter to work with 80V bus?

I referred following circuit from TL431 datasheet TL431 max voltage at cathode is 36V. since circuit has only a transistor , how to modify this circuit to work with 80V at input(Vi bat). output ...
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