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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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Voltage references to keep load cell readings stable

My load cell readings (handled by my HX711) become unstable when I replug the USB cable (which is powering my ESP32-C3). And they become stable again if I reset the ESP32-C3. Someone told me it was a ...
wyc's user avatar
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FLC100 Flux Gate: How does the reference voltage work?

I am using a set of six Stefan Mayer FLC100 flux gate magnetometers to measure a magnetic field along 3 axes. My current understanding of how to use these is that you take the differential ...
matt 's user avatar
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Should I replace my stepper driver since my motor is acting up?

I've been using a Pancake Bipolar Stepper Motor for a project and STSPIN220 as the driver, but I've been randomly having a lot of current issues causing my motor to jitter. My project has been running ...
alxzhu's user avatar
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2 answers
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LDO vs voltage reference when input signal is noisy

I am designing an active EMI-filter (AEF) with an op amp (LTC6227). The AEF suppresses noise from a DC/DC converter. Ther op amp requires a supply voltage of 9V and a reference voltage of 4.5V at the ...
Schafa's user avatar
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How to Properly Select Resistors and Capacitors for a Voltage Reference Circuit with BJTs

I am working on a reference voltage circuit and I am having trouble when selecting the appropriate resistor and capacitor values. The circuit involves OP07 operational amplifiers and transistors (...
Cheche Romo's user avatar
4 votes
3 answers
317 views

Function of R6 in this voltage reference circuit

I've seen the following precision voltage reference circuit in schematic diagrams of several vintage instruments: I understand how this circuit works in general: it is basically two constant current ...
avian's user avatar
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1 answer
153 views

INA125 Reference Voltage lower than expected

I am using a INA125 to amplify the signal from a load cell. When I connect everything according to the datasheet as seen below, the reference voltage drops when I connect the load cell. I am supplying ...
tijnvr's user avatar
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CS1237 ADC - series resistor of voltage reference too big?

I've recently tried multiple times to get consistent readings of a loadcell with a CS1237 ADC-module like the following: https://www.androegg.de/shop/cs1237-24-bit-adc-ad-konverter-modul-tl431/ It ...
Seppde's user avatar
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MDAC AC reference input

I previously had a question on using AC reference voltage with a MDAC, But it has been addressed nicely in the answer below. How does the "Multiplying Bandwidth" specification relate to a ...
Chetan Karkera's user avatar
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1 answer
31 views

Voltage reference 1/f noise datasheet comparison

I would like to compare the 1/f noise of the voltage references LT1021 and LTC6655. The LTC6655 has a spec of 0.25 ppm (0.1-10Hz) and the LT1021 has 3uV_pp (0.1-10Hz). I assume these datasheet ...
Stefan Wyss's user avatar
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Noise density in 1/f region

The datasheet of the ADR1000 voltage reference specifies the 1/f noise density as 30nV/sqrt(Hz) at 10Hz and 300nV/sqrt(Hz) at 0.1Hz. Given that this is the 1/f region of the voltage reference, how can ...
Stefan Wyss's user avatar
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Why use a voltage reference chip rather than a known VCC and resistor? [closed]

To elaborate, I'm making a circuit that converts an analogue sensor output into an on/off state using a comparator. Is there any reason that I should use a voltage reference chip as the low comparison ...
Steam Ranger's user avatar
2 votes
1 answer
61 views

ADS7830 ADC unable to provide meaningful values with 3.3 V external reference

I made a board to read some analog values using an ADS7830 ADC. I wish to use a 3.3 V source as external reference voltage. The schematic and layout are shown below (R6, R7, R14, C4, C5, and C6 ...
Eric Jin's user avatar
3 votes
2 answers
211 views

(TAoE) JFET voltage reference derivation

I've been reading the Chapter 9 of The Art of Electronics, 3rd ed., and apparently the equation I derived for the following circuit is wrong. My reasoning follows. Vout is the sum of the ...
tfm's user avatar
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3 answers
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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 ...
Suvi_Eu's user avatar
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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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1 answer
203 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
128 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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1 answer
84 views

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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49 views

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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1 answer
67 views

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
223 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
77 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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1 answer
48 views

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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997 views

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. ...
kam1212's user avatar
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1 vote
1 answer
151 views

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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1 vote
1 answer
248 views

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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0 answers
154 views

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
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1 vote
1 answer
145 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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0 answers
35 views

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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1 vote
1 answer
129 views

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
265 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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0 answers
53 views

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
0 votes
1 answer
29 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,...
Calvin Gloster's user avatar
1 vote
2 answers
197 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 ...
Confused's user avatar
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0 votes
2 answers
95 views

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 ...
Confused's user avatar
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1 vote
1 answer
235 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
675 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
91 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
314 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
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1 vote
1 answer
921 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
  • 1,016
2 votes
2 answers
522 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
0 votes
3 answers
616 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
  • 2,217
4 votes
3 answers
473 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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