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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253 views

Arduino mega 2560 Analog max reference voltage

Each time I power up the Arduino, the max reference voltage which is represented by 1023 changes. I observed this by measuring the voltage from the Aref pin each time. Is there any internal function ...
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39 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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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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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 ...
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27 views

Moving from ICF in-amp to traditional in-amp, removing bridge offset, driving ref pin with shunt regulator

Right now im using AD8237 with MCP4725 to remove bridge unbalance. I'm using 3x 1k Ohm resistors and one strain gauge arranged in Wheatstone bridge. My circuit looks like that: It works perfect for ...
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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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63 views

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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69 views

Does AREF pin of ATMEGA series consume any current?

I have a voltage reference in the circuit and I thought I can feed that reference to AREF pin of ATMEGA as well: The current at "1.024V" tag is around 200 uA, any current drawn by the AREF ...
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32 views

Programmable sensor signal reference voltage

I'm designing the front-end circuitry for an ADC. The ADC is to be used to read from sensors under two use conditions: An externally referenced sensor, whose signal line will either be 0-5V or ...
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2answers
36 views

Transformer isolation and reference

For testing purposes, I need two circuits: 220Vac rectified and 48Vac rectified, both having the same reference, like this: But I don't have an isolated transformer 220V:220V. I only have an isolated ...
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65 views

Is this differential RC filter needed on a reference voltage?

What is the use of the differential RC filter at the end of this op amp (at least I'm seeing R100+R98+C28 as that)? P3_3V_REF is a reference voltage for the 4 ADCs in the TMS320F28377D-EP MCU. An ...
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38 views

180V voltage reference

I have a 195-210V(with ripple) power supply and I need a 180V voltage reference. This is my best idea so far: Instead of just connecting a resistor and 180V zener diode in series, I do it two times ...
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3answers
52 views

Op amp to supply current to 3 thermistors and an ADC voltage reference input

I have 3 thermistors in parallel that I need to measure. These thermistors will be fast changing - think up to 100C in under 1 second. I want to do this ratiometric measurement, so I want to supply ...
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2answers
577 views

Understanding differential ADCs and reference voltages

The Setup: I am currently prototyping a wheatstone bridge setup to measure small resistance changes. I don't have the sensor I'll be using yet, so I've simulated it using trim pots. I am using a ...
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1answer
201 views

How do I make a discrete voltage detector?

I would like to design a circuit which has outputs LOW when the voltage it is connected to is below a threshold, like 3.3V. There are some ic's you can buy to do this, but I would like to make my ...
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77 views

Vref value and Vref shunt ICs for an ADC

Hello i am building an ADC circuit, this is my first time building a proper adc that is higher performance. The adc is the ADS131 The ADC will be powered by an isolated 3.3v and I would like to know ...
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1answer
51 views

Powering TL431 from MCU output possible?

I'm designing a board with ATmega128 MCU. I have a TL431 reference connected to the ADC_REF pin, with both TL431 and the MCU connected to the same supply, 3.3 V. Now I realized one problem - since ...
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1answer
54 views

Voltage reference voltage drop

I have two potentiometers and a single voltage reference, connecting them causes a few mV voltage drop in the simulator: Adding an op amp solves the problem but then comes input offset voltage and ...
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46 views

Using a Zener to offset split rail?

simulate this circuit – Schematic created using CircuitLab i've searched but can't find a definite answer, is it possible to use the standard resistor divider but with a Zener in the middle to ...
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2answers
81 views

Optocoupler Reference

I want to use in my project an isolated optocoupler like this one to switch an IGBT. In the following schematic, taken from this Vishay application note there's a "floating supply" in Vcc1 as you can ...
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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 ...
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80 views

LED voltage references?

Often reference voltages are generated using normal LED/diode, not zener. A reference from simple resistor divider will not provide any regulation of input voltage, a zener will provide regulation and ...
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1answer
64 views

What is ADC Supply Current in Microcontroller and how much current will a GPIO take

I am having this Microcontroller In this Microcontroller, I am using the ADC peripheral and normal GPIO port. My questions: On Page 58, table 42, There is a parameter called as Supply Current per ...
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81 views

Poor man's voltage reference

I want to build a voltage reference based on LM4040 (A series 0.1%), the output voltage is switchable with a selector switch: simulate this circuit – Schematic created using CircuitLab ...
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1answer
107 views

Voltage Reference Resistor Calculation (Shunt)

I am trying to design a circuit using this LM4040-5 Voltage Precision Reference for my DAC8554, but I can't for the life of me figure out how to properly calculate the resistor value to be applied. ...
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546 views

How to calculate RMS current from the rated current? Are they the same in a stepper motor?

I want to use the TMC2130 driver with the stepper motor I show below. This driver has these main features amongst others: Integrated power MOSFETs handle motor currents up to 1.2A RMS (QFN package) / ...
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2answers
35 views

Noisy output on voltage reference and correct probing

I'm building a circuit that has a 2.5V Voltage reference for use on the internal ADC of a STM32F7 in 12 bit mode. As each bit corresponds to 610uV I'd like to have as little noise in the signal as ...
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24 views

Bipolar voltage reference for DAC AD5791

I am constructing a circuit utilizing the DAC AD5791 from Analog Devices. As shown in the application example in the datasheet, a bipolar voltage reference with +/- 10 V is needed. In fact, the ...
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1answer
142 views

When to add an op amp buffer to a voltage reference IC?

The circuit below is from a TI reference design, but my question is generic. I'm generating a voltage reference to add a DC bias to an AC signal for ADC purpose. Could I use the output of the voltage ...
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2answers
110 views

Voltage reference with op-amp buffer and additional filtering

I commonly see voltage references implemented with op-amp buffers as shown below. That's the simplest way. However, see below another way of doing it which I found in a meter: The second one seems ...
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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 ...
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2answers
685 views

Can I adjust the volume of a DAC using PWM?

Here is a circuit that allegedly converts PWM into a precision voltage reference: (source: dangerousprototypes.com) I am thinking about feeding that reference into the reference line on this ...
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0answers
46 views

TSM104W Voltage Reference

Hi I am trying to design with the TSM104W, which is a 4 package rail-to-rail OpAmps, with a built in voltage reference. This is the package pinout: I see that the four Op-Amps are supplied through ...
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2answers
96 views

Hall Effect Shielding

The objective of the circuit below is to get the difference of the hall effect output and a 1 volt reference, then amplify it. When I first built the sensor and tested it, it worked very well. This is ...
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1answer
34 views

Bandgap References - What's the need for a PTAT voltage if we can invert a CTAT?

I was reading up on bandgap references. I noticed that a CTAT voltage can be simply produced by taking the Vbe voltage of a BJT. However, when generating the PTAT voltage, most books seem to mention ...
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31 views

Current mirror not depending on power supply (BANDGAP design)

is there any topology that allows a current to stay constant on a current mirror when the power supply of the transistor is varied? I simulated a bandgap and the PTAT varies a lot when I the power ...
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1answer
43 views

MCP4725 DAC and reference volatge

MCP4725 has internal reference voltage which is equals to VCC: VDD is the power supply pin for the device. The voltage at the VDD pin is used as the supply input as well as the DAC reference ...
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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 ...
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30 views

Higher order effects of CTAT and PTAT when testing a BANDGAP

I want to use candence to simulate the real behavior of a voltage reference and so far I found circuits that are based on the ideal models. What non linearities can I introduce in this ideal model ...
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35 views

Temperature coefficient of a voltage source

Is the temperature coefficient of a voltage source related to the internal resistance of the voltage source? Why does the voltage increase/decrease when the temperature is increased or decreased? In ...
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1answer
58 views

One voltage reference per DAC or one voltage reference for all DACs?

I have a circuit that requires six 18-bit DACs (AD5680) on it. Each DAC draws ~800µA at the high voltage output +5V and ~400µA at 0V output. Is there any issue with a single REF195 voltage reference ...
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3answers
77 views

Generate accurate 20mV Vref

I want to generate 20mV Vref using Op amp, like this: When simulate with TINA using model from TI, instead of 20mV at output (Vref port), i see that it is 27.95mV. My question is: Why I can't get ...
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4answers
150 views

Does resistance decrease over a resistor?

If ohms law pertains to voltage, current, resistance across a resistor, in order for voltage to drop, and current to remain the same, does resistance drop as well across the resistor? To explain what ...
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1answer
138 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 ...
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1answer
71 views

reading a high negative voltage with attinys running on batteries

I need to read a negative input voltage from a camera flash capacitor that can charge up to -330V. I am using an attiny85V that is running on batteries and want to set the internal reference voltage ...
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77 views

How does one calculate output voltage noise of a current output DAC?

I am using a current output DAC connected to a voltage reference and a transimpedance amplifier. I know the noise characteristics of the voltage reference and the amplifier. The DAC simply lists "13 ...
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140 views

In HLW8012 where should I connect the reference voltage (GND)

In the datasheet of HLW8012, the both 33nF capacitors , 1K resistor and 0.1uF capacitor are connected to GND. I'm not sure where should I connect those ends of components marked with GND symbol, (To ...
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1answer
290 views

STM32F030R8 Nucleo-64 Board ADC Voltage Reference

I want to decrease the reference voltage of the ADC to have a better resolution, by now I do not want to try other options. Could someone explain me how can I do this? I am using the Nucleo-64 ...
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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 ...
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3answers
730 views

What is voltage trimming in bandgap references?

I just started reading about bandgap reference circuits (PTAT, CTAT generation, etc.) in CMOS and I see a lot of papers about something called trimming in relation to these. What does it actually ...

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