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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42
votes
1answer
3k views

What do you need 1.018V for?

The Fluke 732A has among 10V and 1V references also a 1.018V reference (whereas the 10V is the "main" references and the others are formed by resistive voltage dividers). While having multiple ...
25
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4answers
6k views

Why use 2.048V and 4.096 as a reference?

On many voltage reference ICs (As an example a MAX610x) there seems to be various different reference voltages available (1.25, 1.8, 2.5, 3.3 etc). What strikes me as odd are the 2.048V and 4.096V ...
24
votes
6answers
10k views

Voltage regulator vs. voltage reference

I need a cheap, somewhat accurate (~0.5%) voltage reference for some DACs. At first I was going to use a LDO voltage regulator (a TC1223 specifically) for this, it seems to fit the bill looking at the ...
19
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1answer
6k views

AVR 1.1V Internal ADC Reference Over-Voltage

If I use the internal 1.1V reference for the ADC, and my Analog input exceeds 1.1V, lets say 2.5V, is that harmful to my microcontroller? Or will ADC value simply clip (to 0x3FF) at 1.1V? For ...
16
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3answers
7k views

Why is there a 0R resistor linking GND and AGND in analog voltage reference circuit?

This is related to another question I've just posted (What's the purpose of a ferrite bead inductor on this circuit?), regarding the battery charger described in the AVR450 Application Note - ...
16
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3answers
4k views

Why do they make traces to LTZ1000 in spiral shape?

I was browsing Google images of LTZ1000 voltage reference IC. I saw that in some of the PCBs, the traces that go to LTZ1000 are in spiral shape and cut out gaps are left between them. What is the ...
13
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1answer
3k views

Can I use differential I/O pins of FPGA as high speed comparator?

High speed comparators are rather expensive and speed is what FPGAs are very good at. On the other hand, FPGAs (in my case: XC3S400) have paired differential pins in each bank that their voltages are ...
10
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2answers
10k views

ATMega328 External AREF Connection

From the ATMega328 datasheet, section 24.9.1: The internal voltage reference options may not be used if an external reference voltage is being applied to the AREF pin. From the Arduino reference ...
9
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1answer
6k views

Using a Zener diode as voltage reference

I want to use a zener diode as a voltage reference to the the PIC18F2550, as the analog V+ reference. I am planning to use this zener diode, but I am not sure how to calculate its values. I am ...
8
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2answers
9k views

What's the purpose of a ferrite bead inductor on this circuit?

I'm studying the analog voltage reference circuit described in the AVR450 Application Note - Battery Charger for SLA, NiCd, NiMH and Li-Ion Batteries, which schematic is below (copied from page 38). ...
7
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2answers
1k views

LEDs vs. Zeners: what is quiet?

LEDs can be, have been and are used as voltage references. Standard LEDs in various colors are cheap and hence sensible when wanting a low accuracy low voltage reference. Remember that low voltage ...
6
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3answers
3k views

Why do we need many complex voltage references when a zener can do the job

There is a huge variety of Zeners that exist. They have varying breakdown pd among other things. Why then do we need voltage references that are more complex and made up of many components?
6
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2answers
173 views

What are the critical characteristics of an op-amp for buffering reference voltages?

So, let's say I have a precision voltage reference with the output fed to a voltage divider which is tapped at two places for voltages A and B. I've made sure to use precision resistors (or calibrate) ...
6
votes
2answers
21k views

How to calculate minimum zener current if it is not explicitly specified in the datasheet?

simulate this circuit – Schematic created using CircuitLab I'm going to use 1N4740A as a voltage reference in a similar way you see in the schematics above. In textbooks, a zener property ...
5
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3answers
8k views

How does this opamp circuit act as “good” voltage reference?

If I understand correctly, we are using MC1043 because we don't trust Vcc to be stable. I get that the output of MC1043 is 2.5V which is extremely stable. But I don't get how the output of opamp ...
5
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4answers
2k views

Capacitor after Voltage Reference “for stability”

I've got a lot of experience with rather "low-level" electronics (resistor networks, passive filters, basic op-amp circuits) and some experience with higher-level stuff like micro-controllers, but I ...
5
votes
3answers
4k views

Understanding a circuit for reading current passing through human bodies

I found on Instructables this circuit that is used to detect when two conductive pads are touched at the same time by a person (or, in that particular example, a chain of people). Used in conjunction ...
5
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1answer
330 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 ...
5
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3answers
2k views

Why is 4.096V so often used as a voltage reference?

I get that each mV is equivalent to a bit in a 12-bit ADC, but why is 4.096V used so often? I've heard of this being from a "bridge". What does this mean and what is the historical significance?
5
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1answer
527 views

Why does a buffer op-amp need two feedback paths?

I am designing a linear voltage source. I have a precision volatge reference (REF5050 by TI), and before I do anything with its output I buffer it. However, the datasheet of the amplifier I use (...
5
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1answer
3k views

ATTiny Default AREF

I am trying to get the Adafruit Electret Microphone Amplifier to work with an ATTiny85 but am having some trouble with the reference voltage. I am using a 5V circuit because I am also powering a strip ...
4
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2answers
310 views

Learning about voltage references

I want to study the bandgap voltage reference and use it in somewhere. But first I would like to learn more about the basics of generating and using voltage references (mostly for operational ...
4
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1answer
240 views

Precision Adjustable Voltage Reference

Can a low-cost, low-resolution RDAC and a precision voltage reference by used to make a coarsely adjustable high-precision DC voltage reference? Consider for example the AD5121 7-bit RDAC with ±5ppm/°...
4
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2answers
240 views

Why do some voltage reference ICs (LM385B) have 8 pin packages where 6 pins are NC?

A search for voltage reference LM385B reveals that most of its many versions come in either 3-pin TO packages or 8-pin SOIC/TSSOP packages. Very few are 3-pin SOT-23 packages. I was wondering why is ...
4
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1answer
2k views

Strange oscillations with TL431 voltage reference

I have a problem with TL431 voltage reference circuit: There is no load connected to VREF25. When I remove C8, voltage VREF25 is perfectly stable 2.5V. But when I put C8 back into the circuit, ...
3
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2answers
6k views

What is the function of this circuit?

Just wondering if someone can give me an explanation for this capacitor layout - what is it's function? The chip to the right is an ADC. Circled in blue. I'm guessing it is well known but i don't ...
3
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3answers
107 views

Second Order Filter with DC offset

The circuit below takes the signal from a current transformer, depicted as I1, convert it to voltage through R9 and go to the second order filter U1. I want to add an offset to the current transformer ...
3
votes
3answers
1k views

how voltage references work - LM336

In the datasheet for the LM336-5.0 5V reference it uses a 5k resistor fed by 10V. Am I correct in saying that I can give it 12V and it wouldn't matter as long as the current is limited to less than ...
3
votes
1answer
137 views

Grounding an audio signal

I'm building a simple audio mixer. It's going to be running from a USB power supply, so I'm using a TLE-2426 to derive a 2.5V reference voltage for the summing op-amp. My question is, what do I ...
3
votes
2answers
513 views

MCP1501 Voltage Reference has very noisy output

I want to use the MCP1501 precision voltage reference in an ADC circuit and have the issue that the reference produces a very noisy output. Much worse than an average LDO. I have a VPP of 200mV when ...
3
votes
2answers
966 views

Flip a Schmitt-Trigger when current flows through a Zener diode

I am trying to design a circuit using an intermitent power source (a bicycle hub generator), which is rectified and filtered, and regulated at 6,8V. Now I want to "detect" when the power source is ON ...
3
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3answers
809 views

Optimizing Resistor Values for Comparator Reference

Curious if there is a general rule for optimizing total resistance values in a voltage divider reference in a comparator circuit. Guessing it ultimately comes down to whether maximizing accuracy or ...
3
votes
1answer
1k views

For which frequency is ESR specified by default?

I'm playing around with an REF5010 voltage reference, and its data sheet specifies an output capacitor with an ESR of 1 to 1.5Ω for best performance. Now when I measure the ESR of electrolytic ...
3
votes
2answers
2k views

ratiometric ADC, is it feasible to separate reference voltage and excitation voltage by an amplifier

I have a variety of bridge transducers (pressure, strain gage) with sensitivity of 1mV/V. Also, most 24-bit ADCs and analog frontend chips have a PGA with programmable gain between 1-128. This means ...
3
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2answers
11k views

STM32 ADC reference voltage

I'm using STM32 F7 46 (reference manual) and I'm a bit confused about ADC and reference voltage (VREF). If I connect 2.5V to the VREF and 3.3 to AVDD, then what is the range of ADC measurement? Is ...
3
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2answers
1k views

Design Decisions for using ADC with no VREF

I was looking at Freescale's KE02 processor family, and the MCU designers made an interesting design decision revolving around the ADC that I can't completely wrap my head around. The KE02 has an ...
3
votes
1answer
895 views

How to connect the power for VREFSD pin and anlog pin in STM32F3273 (ARM Cortex-M4) for SDADC application?

I have an analog amplifier which is powered at single-supply power and have an analog ground of 1.25V. I want to perform sdadc for my analog output. I am using STM32F373 (48pins), which is an ARM ...
3
votes
1answer
1k views

VREF of FPGA should be grounded if not needed?

I just started FPGAs. I know that Vref is designed for I/O Banks specially needed for some I/O standards or weak keeping. If I dont need them should I ground these pins or leave them floating( not ...
3
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2answers
2k views

HX711 on-chip analog supply regulator, my mistake or datasheet mistake?

Most HX711 boards use an external transistor to supply regulated power for the load cells, the voltage output (called VAVDD) is calculated using this formula from the datasheet: VAVDD = VBG*(R1+R2)/R1 ...
3
votes
1answer
201 views

Backward measurement of AVcc against reference voltage connected to ADC input

what you think about ADC backward measuring supply voltage in microcontroller? It looks interesting for battery-powered devices. The idea is: Connect constant voltage (some voltage reference IC) to ...
2
votes
3answers
978 views

Generating various reference voltages in a circuit

How does one go about accurately setting reference voltages at various points in a given circuit (e.g. various threshold voltages). Obviously we can have a potential divider from the main power supply ...
2
votes
2answers
216 views

Micro-Voltage Reference

I need a micro-Voltage reference to calibrate my micro-Volt amplifier. The ICs only go down to 200mV, fixed. So how should I go about this? Use the lowest I could find, then use a Voltage Divider to ...
2
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3answers
361 views

Accurate -2V reference

I have an old Keithley 175A multimeter that has been suffering from a bit of drift lately. Internally it uses a 6.35V zener and a couple of resistors to create a -2V reference, but the zener is ...
2
votes
2answers
574 views

Faster settling time for near DC pole low pass filter

I need to clean up the noise from a voltage reference and I wanted to use a simple RC low pass filter. In order to lower the pole position I have to use a big resistor and/or a big capacitor. As the ...
2
votes
1answer
194 views

Can I cascade voltage references to get better stability?

is it possible to get higher output voltage "stability" by cascading voltage references? -- REPHRASING -- Suppose I have IC1 and IC2. Both are 0.5% accurate TL431 parts. IC1 takes 15V and outputs ...
2
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2answers
454 views

PIC 18F: Can A/D (+) Reference voltage exceed Vdd?

I am considering using Pololu's P-Star 25K50 dev board for some simple LiPo cell testers. This board is a complete system with on-board voltage regulator, USB micro-B jack and the Microchip PIC ...
2
votes
2answers
328 views

How improve temperature sensitivity of HP 721A DC Power Supply voltage reference?

I have a sentimental affection for my HP 721A DC Power Supply: http://hpmemoryproject.org/pict/wall_a/anim/721a_q90/viewer.htm Rugged, dependable, and roughly as old as I am, it is also pretty ...
2
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2answers
1k views

Voltage Reference Output Impedance

Relevant Datasheets: AS431 Voltage Reference INA126 Instrumentation Amplifier I am designing a circuit which will amplify a few millivolt input (~+/-10mV full range) to a few volts (~0-8V output, ...
2
votes
2answers
552 views

Which resistor watt rating to use for this circuit and Arduino 5V?

http://www.skillbank.co.uk/arduino/measure.htm I am looking to build the circuit this guy recommends for making a better analog reference source. I found the voltage reference diode, and now I am ...
2
votes
2answers
537 views

What half-bandgap voltage reference is?

I came across term "half bandgap voltage reference". I expect it is somehow related to bandgap circuit. Do you know what it is, know its schematic or principle of operation?

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