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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How a REF102U precision voltage reference works? [closed]

I'm looking at the circuit schemes in which a precision voltage is used. I have never worked with them before. I have read some literature and, obviously, its datasheet: REF102U datasheet I didn't ...
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How to isolate audio signals from each other using op-amps with the same single supply?

Reuploaded corrected picture, as the old one was with confusing ground connections: I am new here, so please be patient if I'm doing something wrong. I really need some help as I can't figure it out ...
Manac's user avatar
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Understanding reference levels in circuits

I understand that a zener diode uses its anode as a reference to limit the over-voltage levels that appear on its cathode. However, in the circuit shown below, I am confused about why the anode of the ...
Momobear's user avatar
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What is the purpose of the 400 kΩ resistor in the 7 V positive reference circuit of the LTZ1000?

This circuit is from the datasheet of the famous LTZ1000 voltage reference: Can anyone explain in detail how the circuit works? Especially the 400 kΩ effect; what is the benefit of the 400 kΩ ...
jsuarezbaron's user avatar
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176 views

What is the best and simplest way to generate multiple accurate reference voltages?

I need several reference DC voltages to use them to calibrate hundreds of circuit boards manufactured in our facility. The voltages to be calibrated are 5V 10V 100V 200V 500V The accuracy required ...
AlMoutaz Billah's user avatar
1 vote
2 answers
113 views

Using a low power reference voltage source to regulate higher power supplies

I want to put together (1) a cheap home breadboard reference current supply to calibrate and test 3 1/2 digit DMMs and (2) a low noise power supply to replace batteries in battery-powered audio ...
Sara's user avatar
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Voltage Regulation Techniques and BJT Usage in LT4363

There are instances when the input voltage is utilized to power a chip, and the maximum voltage (VCC) allowed on the chip is lower than the input voltage. In such cases, I consistently use a Zener ...
chami's user avatar
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Non-inverting amplifier with offset

I have a non-inverting amplifier circuit shown in picture. This circuit has an input wave (-/+ 5V) and output needs to be 0 to 3.3V. I'll be using zener diode (LM 385) as my voltage reference. But I ...
luffy's user avatar
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What is the purpose of these capacitors connected directly to the OpAmp output?

I am studying this schematic and I come across the following section: As can shown capacitors are connected directly between the Op-Amp output to the supply (5V). What is the purpose of these ...
Zhi's user avatar
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How do I connect the reference pins from a microcontroller's internal ADC?

I am using a TMS320F28379 microcontroller with these pins: They are the references for the ADC. Can I leave them unconnected? Do I have to connect them to a specific value? In that case, how I know ...
Developing Electronics's user avatar
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Understanding the purpose of REFT and REFB on a differential ADC

I am using the Analog Devices AD9238 ADC for a project and I am confused about the purpose of the differential voltage references (REFT and REFB). I am powering the AD9238 from a +3.0V supply and I ...
Bertus's user avatar
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Reducing Reference Voltage Error in Accelerometer and ADC Circuit

I am utilizing a specific analog Accelerometer ADXL354 and an ADC AD7682. Currently, I drive the REFIN-Pin of the ADC with the reference Voltage supplied by the Accelerometer. According to the ...
Daniel's user avatar
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3 votes
1 answer
200 views

LM4040 pinout not matching reality vs datasheet

I bought some voltage references from the LM4040 family, NFC41I and NFC20I i.e. ...
herhor67's user avatar
2 votes
1 answer
55 views

Precision voltage reference (LT1236-5) trimming range

I am trying to use this voltage reference in a circuit. I am trying to understand the trimming part of the chip. On the datasheet, one care read the following: The precise relation between the output ...
UnstableDynamics's user avatar
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I need to calculate the bandgap voltage in terms of threshold voltage mismatch (circuit shown in figure). Does my equation look correct?

I computed the change in current due to threshold mismatch, in my assignment question they asked us to express the bandgap voltage due to delta Vth in terms of gm. Does this look equation look correct?...
user124713's user avatar
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UCC3895- VS UC3842-based SMPS designs

I have a slight confusion regarding the UCC3895, which is a four-channel wave generator. Earlier I had worked on the UC3842 and therefore to see better results I wanted to take a look at the UCC3895. ...
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UCC3895 based power supply Confusion

I was working on the UCC 3895 IC in order to work on an SMPS design. I've seen the schematics of the IC and I could find any internal reference as done in some other PWM ICs like the UC3842 having ...
kam1212's user avatar
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External voltage reference MCU RP2040 - Use of series reference?

I designed a board that uses the RP2040 Pico for its ADC and I/O. To improve the ADC of RP2040 I wanted to use an external reference. In the past, for other projects, I used as external reference a ...
Kostr's user avatar
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Monitoring VREF+ buffer output in STM32L552

I am working with the STM32L552 microcontroller in a critical application where a portion of the external circuit relies heavily on the 2.5 V VREF+. The stability of this reference voltage is ...
tronhawk's user avatar
1 vote
1 answer
128 views

Analog design - current sourced by a voltage reference

I am studying the schematics of an analog isolator with variable gain SIM 984 from SRS, the isolator is bipolar and can handle positive and negative voltages. In the isolation part of the schematics (...
UnstableDynamics's user avatar
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Vref circuit design for ADC/DAC

I don't understand calculation and circuit design of external Vref circuits for ADCs/DACs (topic 13.7) in opamps for everyone design reference by Ron Mancini. How to be s=C2R2? How to be determined ...
bb0667's user avatar
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What's the usage of the reference voltage in voltage-referenced I/O standards?

In FPGA I/O resource user guides, there are many places mentioning the "reference voltage" in different IO standards, and how the IO bank can provide such reference voltage to meet the ...
bruin's user avatar
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1 answer
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Which topology of power regulator gives a stable voltage output, linear or switching?

I am experimenting on the stability parameter of switching vs linear regulators. By stability I mean how much the output voltage ripple is changing. A lot of online reading has made me understand that ...
JustJuan's user avatar
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1 answer
187 views

Voltage reference vs voltage bias for EOG circuit

This is continuation of my previous question. I'm confused about the reference voltage and bias voltage. As seen in the image above, the supplies for the INA333 and OPA2335 are clearly 3.3V and ground....
roaibrain's user avatar
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Switching reference voltage with capacitor on AREF

I do two conversions (ratiometric measurement) with AREF = AVCC = VCC = 3 x AAA battery. AVCC is connected to VCC via an LC network as recommended in the data sheet of the ATmega328P. I would like ...
Torsten Römer's user avatar
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1 answer
28 views

Voltage reference required for DAC81404

I want to create a driver board to control a piezo actuator. I have a DAC81404 DAC laying around, but I am confused as to how the voltage reference works. I want to drive the piezo from -15 V to +15 V,...
C Geeeee's user avatar
1 vote
2 answers
156 views

Generating a solid 5V output from a buck converter whose output varies from 4.8V to 5.2V

I have a buck converter whose output varies from 4.8V to 5.2V. This buck converter is present in my VCU. Input for the buck converter can vary from 8V to 14V. The 5 volt rail is powering many IC's ...
Hari's user avatar
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2 answers
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LT1389-5 voltage reference output is not as expected

I am using the LT1389-5 for one of my projects. My circuit is given below. For 5 V output the maximum operating current is 10 mA. This is obtained from the maximum ratings. I calculated the value of ...
Hari's user avatar
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1 vote
1 answer
168 views

Power MOSFET vs power BJT (Darlington), which has less noise?

I have an initial accurate voltage reference, which I need to buffer. So I feed it to an opamp, which then drives a final output power transistor for a high current final voltage reference. Of course, ...
Tempus Nomen's user avatar
6 votes
4 answers
598 views

Precision current source and mΩ measurements

I'm trying to measure some resistors in the 3-5 mΩ range. I want to use a precision current source (picture below) and an AD7791 ADC for that purpose. I also want to use a 1.2 V reference voltage (...
Tolik4's user avatar
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1 vote
2 answers
81 views

Does initial accuracy tell us anything about output voltage drift with reference voltages?

Consider the ADR421. From the data sheet the initial accuracy is shown to be + or - 3mV of the nominal (2.5V). I understand that if you power on one of these chips with conditions at 25 degrees C, Vin ...
BobaJFET's user avatar
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5 votes
1 answer
312 views

Meaning of long term stability unit (µV/mo)

What does 'mo' stand for in a long term stability spec which has units of μV/mo?
Efanatic's user avatar
1 vote
1 answer
494 views

Voltage reference drift in ppm/°C to V/°C

How does one convert drift in ppm/°C to V/°C? Assume a 5 V voltage reference has an output voltage drift of 12 ppm/°C. What is the output voltage drift in volts for a target temperature of 85°C?
Efanatic's user avatar
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1 answer
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How does this voltage refence work?

Regarding the left side of the circuit: There is a fixed 1.2V voltage reference and a potentiometer for the input. What could be the purpose of the voltage reference in this case? And what is the ...
ty_1917's user avatar
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2 votes
2 answers
400 views

Precision voltage reference for ADC

I'm designing a precision voltage reference for an ADC. The aim is to sample a 230 Vrms AC signal using the STM32F411 built-in ADC. An opamp-based differential amplifier is used to convert a 325 V ...
Vivek Vijayan's user avatar
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3 answers
461 views

Why is the Vref of the DAC used in the op-amp amplifier stage?

I can't figure out why the refence voltage of a DAC is used in the amplifier stage in many circuits. Here are some examples: Why is Vref of the DAC used in the op-amp amplifier stage? Does that have ...
cm64's user avatar
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4 votes
3 answers
442 views

Unstable voltage reference after changing DAC

I have developed a DAC-based signal generator board that I want to use to generate sine waves of different amplitudes and frequencies. The board was working but unfortunately, the digital-to-analog ...
Mau5's user avatar
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0 answers
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How do I get a 1.5 V reference voltage from a 3 V coin cell battery? [duplicate]

My goal is to build an amplification circuit powered by a 3 V coin cell battery that uses an instrumentation amplifier to read a differential voltage. The instrumentation amplifier chip has a ...
dinoswords's user avatar
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0 answers
66 views

What is the statistical accuracy of a Reference Voltage based current source?

I would like to make a current source from a reference voltage chip (REF102). OPA277 is used as a buffer to pin the voltage at pin 4 to the bottom of the current setting resistor R. Hypothetically, if ...
Efanatic's user avatar
1 vote
1 answer
196 views

Low Noise - High DC Accuracy Voltage Reference Buffer ? Composite Amplifier?

I want to built a low noise voltage reference buffer to drive an ADC and additional analog circuits. Main requirements: "Ultra"-Low Noise Best DC accuracy possible (mainly interested in ...
huababua's user avatar
6 votes
3 answers
1k views

How to use a signal generator to provide a clock for a floating microcontroller?

If a microcontroller circuit is powered from a floating 3.3 V supply, what is a safe way to use an external instrument such as a signal generator to provide a square wave into the microcontroller's ...
user882326721's user avatar
4 votes
2 answers
877 views

What is exactly a "stabistor"? How does it work and how is it constructed?

Today, for the first time in my life I encountered the term "stabistor". From a quick search on the Internet it seems it's a two-terminal diode-like semiconductor device used to regulate low ...
LorenzoDonati4Ukraine-OnStrike's user avatar
0 votes
1 answer
72 views

How to find accurate reference voltage and how to set them to ADCON register of PIC10LF322?

I am a beginner who is interested to learn more about PIC controllers and currently I am working on a small project to turn ON an LED indicator based on the input voltage. I am using PIC10LF322 and I ...
Nithiya Shree's user avatar
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1 answer
88 views

Is there a way to activate a precision reference voltage via software without compromise?

I'm working on a project where I need to activate/deactivate a precision reference voltage depending on the situation. I was thinking about using either an optocoupler, a MOSFET, or a transistor, but ...
s.1.618's user avatar
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1 answer
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IOREF default voltage reference circuit with two NPN transistors

I'm trying to build a small circuit to sense when a voltage ref (for IO output) is supplied otherwise set a default voltage reference. A bit of context - This is common within the Arduino ecosystem ...
Shlomi Hassid's user avatar
4 votes
2 answers
652 views

Voltage reference circuit with op-amp and Zener diode

I am looking at the voltage reference circuit used in a source measurement unit, which is meant to be stable and precise: The circuit above is said to be a 10V reference as described in the block ...
ONLYA's user avatar
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7 votes
5 answers
2k views

Why can't a P-N junction diode be used as a voltage regulator or reference in forward bias?

Usually, a Zener or avalanche breakdown region for a suitably doped P-N junction is used for voltage regulation as a substantial variation in the current (due to minority carriers) requires a ...
ThePhysicist's user avatar
2 votes
1 answer
84 views

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 ...
lepton-7's user avatar
3 votes
1 answer
222 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 ...
ElectronSurf's user avatar
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0 votes
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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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