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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50 views

switch 3 references voltage for my servo position

I have some positioning servo driver and servo with pot feedback. Now I try to build circuit to switch between 3 positions. For testing I just use 3 way switch and 3 pots as voltage reference, but in ...
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152 views

Using a voltage divider with buried zener voltage reference

My plan in the below circuit was to use a voltage divider from a Max6225 2.5Vref, to get 2V and 1V from it in order to use the full 16bit bipolar scale of the ADS1115s, but I'm getting strange ...
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238 views

DAC negative bias reference voltage

I'm using TI's 18-bit DAC9881 and need the output to go a little below 0Volts in order to account for offset voltages of following Op-Amp stages. The DAC allows to provide a "low reference" between -...
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How can I create a fixed voltage reference output voltage from a varying input voltage?

Suppose I have the following: A voltage source that outputs a voltage between 10 and 14 V. I need to generate a fixed reference voltage independent of the input voltage mentioned above. How can I do ...
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343 views

Reducing noise on a voltage reference

I need a stable, low noise voltage reference that I can adjust between 1.4V and 1.8V. The output should source or sink up to 0.25mA @150Hz max. The output will provide a +1.65V bias for a bipolar ...
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163 views

LM317 Vout drops on load

I built a very basic circuit to get around 5.5V from a +15V source I have a 220 Ohm between Adj and Vout and one 470 Ohm, one 220 Ohm and two 100 Ohm in parallel between Gnd and Adj summing up to ...
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743 views

Negative Voltage Reference for Bipolar ADC

I am considering using ADS1258 - a bipolar ADC. It needs an external reference across REFP(+) and REFN(-). How do I generate precise -2.5V assuming I have +12V and -12V analog voltage rails? I can ...
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271 views

Using positive voltage reference on a negative supply

Got a 9V,0,-9V power supply and want to get two stabilised voltage references at 2.5V and -2.5V. Is it possible to use a +2.5V reference chip "upside down" to supply the -2.5V?
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102 views

REF02 not working - 4 channel 5v DAC circuit, star gnd connection, stripboard layout

I've connected my circuit as in the diagram, with a 15V PSU powering it (both amps are connected the same way) - but the DAC seems to be drawing too much current for the REF02 to handle, even though p....
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972 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 ...
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173 views

build 2V reference with 100mA output

Consider I have a 2.048-volt reference voltage, for example, I build this voltage with REF191, this IC has only 10mA output current, How can I boost this current to 200mA? is there any better way to ...
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Voltage reference TLVH431

I started working with the LT1990 Differentiel amplifier. In the datasheet, it's stated that it needs a 1.25V voltage reference. I made some research and I found the TLVH431 Low-voltage adjustable ...
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369 views

Generate negative reference voltage

In my current design, I need to include force measurement. A301 sensor is selected for this. Now, in order to be able to have analog voltage proportional to the force applied, I need to have negative ...
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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 ...
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156 views

What's the PIC FVR's gain amplifier settling time when you change the gain

I previously had configured a PIC (16F1704) to use the internal FVR for ADC reference, with gain of the FVR set to 2x, i.e. 2.048V reference. I've since added another signal to be measured, but the ...
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46 views

Loading reference output of an ADC

My ADC (LTC2323, 16 bit, 5MSps, http://www.linear.com/product/LTC2323-16) has an internal reference (4.096V) which is provided at output pins REFINTx. Now I need (...
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3answers
578 views

Do the temperature coefficients of the resistors in the LM399/LM199 “Portable Calibrator” significantly effect the output stability?

I'd like to know how voltage reference stability is obtained in products like 6.5 digit multimeters that use LM399 as a voltage reference in spite of using two gain resistors. Let's assume an ideal ...
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890 views

Resistor Between Voltage Reference and + Input of Op-Amp? Why?

something I commonly see in schematics which include op-amps set up as inverting amplifiers is the inclusion of a resistor between the non-inverting "(+)" input of an op-amp and a strong voltage ...
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3answers
481 views

How an op-amp determines its output without a reference point? [duplicate]

I was struggling to understand how an op-amp determines its output without a reference point. The output of an op-amp is A * (Vni - Vi) Then let's say we have an inverting op-amp with a gain of 1000,...
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776 views

Is a diode's forward voltage stable enough to be used as a reference voltage?

Assuming a resistor is in series with a diode (say, a 1N4001) so that the diode has around 1mA of current, will its forward voltage be usable as a voltage reference to within 1% (relative to itself ...
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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) ...
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235 views

ADC Vref Options [closed]

Looking to utilise vref on a K60 Kinetis, which has VREFH and VREFL pins. Ideally referencing to 3v3, but very stable -ie not using the supply lines - what would be the best way of achieving this - a ...
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1k views

Why is the reason of using BJTs instead of diodes in Bandgap references?

I'm just asking what is the main reason to use BJT transistors as pn or np junctions for bandgap voltage reference instead of using just pn or np diodes also available on CMOS technologies.
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747 views

How do you generate a reference voltage in a circuit?

Hi Im very new to electronics and had a pretty basic question about voltage reference. So Ive finally understood that in order to check a voltage in most circuits, a voltage reference is used. The ...
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188 views

Configuring Arduino to use external ADC reference for Analog inputs through MATLAB support package

I am using the MATLAB support package for Arduino. However, I need to configure the ADC reference to external. MATLAB documentation doesn't really explain how to do this? Is there any way I can use ...
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104 views

ADC not referencing to 4x fixed voltage referenced - PIC16F18854

I am using a PIC16F18854 with a stable VDD of 5.0V. Tried multiple chips. Code has been primarily generated using MCC and verified with the datasheet. Applicable registers: ADREF: ADNREF = VSS, ...
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215 views

Supply topology for microcontroller and ADC/sensor with noisy input/outputs

I am experimenting with a microcontroller project with a very wide-ranging, noisy DC input voltage at VCC. The controller processes a sensor input to the ADC and outputs a pulsed signal on all pins of ...
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2answers
376 views

AT32UC3C Negative ADC Input Voltage

The AT32UC3C ADC can be set up using either internal or external references as seen in Table 36-8. For any type of voltage reference used, the datasheet suggests that the ADC is capable of converting ...
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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, ...
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2answers
407 views

Is there a simpler way to create a variable voltage drop than a differential amplifier?

I am working on a preregulator circuit design (it's derived from the one in LTC AN32), and am trying to design the test fixture for it. Two of the three components are clear: I can use an AC-output ...
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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 ...
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173 views

Increase accuracy of ADC without device AGND

I am using the ADC of the PIC16F18344 — http://www.microchip.com/wwwproducts/en/PIC16F18344 It has neither Avdd nor Agnd, but it does have selectable Vref+ and Vref- pins. If I were to stop using ...
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2answers
196 views

ADC variable reference voltage

I'm working on a design which must read temperature using RTD pt100 with at least 0.5 degree Celsius accuracy in the range -10 to 50 degrees . I want to use AD7705 ADC. my design looks like this. I ...
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1answer
82 views

Should one terminal of the AC source be grounded?

Is ground physically 0V or just a reference (like maybe 2.5V) that we use to measure voltages from? Should i be grounding the VSINE or just take the voltage across it without the reference. Basically ...
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82 views

Connecting the instrument to two different power supplies

I am very new to electrical engineering and this is my first project on it, so any help would be really great:) I am currently trying to power an instrument, which consists of: 1) Two LEDs 2) Two ...
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3answers
747 views

Set a reference voltage: using a zener diode vs using a buffer

Given the following hysteresis comparator circuit: simulate this circuit – Schematic created using CircuitLab R1, R2 and OA1 are used to set a reference voltage for the comparator with ...
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3answers
150 views

Input voltage range for lm336z-5.0?

I want to use lm336z-5.0 as a reference voltage for Arduino Uno. In the data sheet I see an example of the chip being connected to a 10V source via a 5k resistor. In Absolute Maximum Ratings section I ...
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3answers
176 views

How are voltage references established in low-power designs?

I've learned that most Zener diodes require something on the order to 20mA in reverse bias in order for Zener breakdown to take place. However, devices such as the LM431 "Adjustable Zener" can begin ...
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3k views

Voltage Reference using OpAmp

I want to create a 0.8V reference derived from 5V using voltage divider and buffered using OPAmp. This is my schematic I will be using this voltage reference for signals upto 10 Mhz (in peak ...
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1answer
172 views

LT1019 voltage reference output 5V to 3.3V

I have LT1019ACN8-5 IC output is 5V. I am using this IC to get Vref 3.3 for the ADS8320. is it ok if i use a voltage divider to the output pin to regulate 5v to 3.3v. Is it acceptable ?
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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 ...
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1answer
149 views

Voltage reference that can drive current in both ways

I am designing a device that at some point needs an oscillator in order to work. The whole circuit is fed by a 9 V battery. The V20 label corresponds to 20 V coming from a Boost converter whose input ...
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6answers
261 views

LM385Z-2.5 in series with voltage divider - voltage reference problem

I'm doing a simple circuit using LM385. In THEORY voltage measured on cathode of D2 should be 5V. And it is so, if R2 and R3 are not present in the circuit. So voltage divider from R2 and R3 across ...
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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 ...
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269 views

Can anyone explain me how the voltage divider network works?

Can anyone explain me why the voltage of the red circle is 1.85V? I know how the 25k-25k divider works but just don't know how the +5V-200k network affects the result.
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Adjustable dual voltage level shifter by using a single potentiometer

I'm very new to the topic but I read that some reference pins of some ICs should not be fed by voltage dividers because of impedance issues. I need an adjustable +-4V output from an opamp or any ...
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1answer
174 views

Trying to multiplex voltage reference gives incorrect output

I'm trying to make the voltage reference for an INA214 opamp selectable between GND, 4.5V and 10V. I'm using a CD4051B multiplexer. However, the 10V VREF gets pulled down to 5.84V, and I can't figure ...
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174 views

Switching between GND and 10V VREF?

I have a bi-directional current sense opamp (INA214), where I'd like to alternate the VREF between GND and 10V. Page 22 ("9.2.2 Bidirectional Operation") in the datasheet has more information. I also ...
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3answers
203 views

Need help understanding this op amp/BJT configuration to troubleshoot why I'm reading different voltages than expected

I am building this VCO in an attempt to study it and I'm having trouble understanding the references section seen bellow. I have used a KIA431 that I 'stole' from a broken switching power supply on ...
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1answer
118 views

Rbias for Vref for ADC

Hi guys I want to verify some calculation. I want to use a Voltage Reference for the ADC (ATmega2560). In the datasheet(on page 11) for the voltage reference is the formula...