Questions tagged [dac]

A DAC is a Digital to Analog Converter.

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6 votes
1 answer
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Why my DAC works without GND and VCC?

This is the most interesting thing I have seen! I have built a DDS that sends data (D0-D7) to a DAC (ADV2175). The design worked fine and I just have a low frequency alias noise (a question here). ...
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23 votes
1 answer
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What is this squiggly trace for?

It's on pin 14, which is the master clock input (MCLK) of a WM8761: Low cost stereo DAC. I'm guessing it's meant to act as a small inductor? But why would you want that on a clock input?
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17 votes
5 answers
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how determine the RC time constant in PWM digital to analog low-pass filter?

I 'm looking for the best RC time constant and its reason in a PWM to convert digital signal to analog based on duty-cycle and frequency and other parameters. PWM frequency is 10 kHz.
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6 votes
2 answers
8k views

Smoothing a High Current PWM

I am using a MOSFET to control the average voltage to a device by varying the duty cycle to the base as shown in the diagram below. My question is what is the best circuit to use in the "filter box" ...
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2 votes
1 answer
277 views

Construct a post-equalizing circuit to compensate imperfect of the DAC

The post equalizing circuit is shown on above. How do I determine the value of the capacitance? I couldn't find any equation to determine it. It have been advised to use LT6202 to construct it, data ...
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22 votes
2 answers
34k views

What is a brownout condition?

I'm reading the datasheet of this DAC. Page 27 states: In many industrial process control applications, it is vital that the output voltage be controlled during power-up and during brownout ...
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16 votes
4 answers
14k views

What is a one-bit ADC good for?

I have recently heard of the concept of a one-bit ADC, and have seen it implemented in the context of a sort of digital-to-analog converter (oddly enough), and I'm wondering, what is the point? Why ...
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13 votes
1 answer
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PCB microcontroller layout in a mixed-signal system

This is a direct continuation of this question. So here's my layout, what do you think about the microcontroller side? UPDATE April 2019: I built the board in spring/summer 2016, but never got around ...
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3 votes
2 answers
3k views

Resistor DAC and buffer for VGA output

I'm in the process of designing a very simple binary weighted resistor DAC for an output stage of a RGB VGA driver. There will be 3 bits for R and G components and 2 for B. The output signal is analog ...
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2 votes
3 answers
1k views

Omp Amp Design for shifting a voltage range

My DAC can only output voltages between 0-5 V and I want to linearly shift the range to -2.5 to 2.5 V. For example, a 2.5 input would (ideally) lead to a zero volt output. Likewise, a 5 V input would ...
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2 votes
2 answers
1k views

4-20mA output/transmitter? [closed]

I've got an MCU with a 3.3V DAC onboard and I'd like to convert the 0-3.3V signal to a 4-20mA output. Any ideas on how to do this?
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1 answer
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How do I remove the offset from the DAC output and change the range?

This DAC has an output range of 1-3 volts. Here's the datasheet: Datasheet I'm getting pulses with different amplitudes, frequencies, duty cycles and widths varying from 0.2 ms to 2 s from the DAC. ...
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16 votes
8 answers
7k views

Is it possible to combine two 8 bits DACs together to create a 16 bit DAC, one byte of the 16 bit word shall be sent to each of them

For two DACs, one being sent D0-D7 and the other being sent D8-D15, with power supply being 5V, if 5V is added to output of 2nd DAC and then the two DAC outputs are summed, should result in a 16 bit ...
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11 votes
4 answers
3k views

Different ways to digitally control an adjustable SMPS

I want to make a battery powered, adjustable SMPS for use in situations when I cannot have an outlet near me, so I would like some more information or suggestions about this topic. The SMPS chip I am ...
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4 votes
3 answers
4k views

Picking a DAC for an audio amplfier

I'm trying to use a specific audio amplifier, TPA3111D1, to power a 10 watt speaker from a microcontroller. I would like to generate sound from a microcontroller that doesn't have a built in DAC, so ...
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7 votes
4 answers
1k views

Counteracting Sound Card AC Coupling for Reading Digital Data

Disclaimer: I am new to EE. Everything I have learned so far I have taught myself from reading online and posting questions like this while working on this project. I apologize if I do a poor job of ...
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  • 231
7 votes
1 answer
3k views

What does "limit cycle" mean in delta-sigma modulator?

Could anyone explain limit cycle related spurious tones? It is stated that a higher order modulator is better than low level one because of limit cycle related spurious tones, but I don't have picture ...
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0 votes
1 answer
5k views

Ground loop isolation of a USB-powered device

I have a device (Device 1) that is bus-powered via Full-Speed USB and that is drawing up to 400 mA from a laptop. Device 1 has a DAC that can output an analog voltage to another device (Device 2) ...
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  • 117
6 votes
4 answers
3k views

Different decoupling capacitors in parallel

Page 29 of this DAC datasheet gives a typical operating circuit. I notice the power supplies have two decoupling capacitors in parallel: 100nF and 10μF. What caught my eye is that there is a ...
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3 votes
1 answer
4k views

How to interface this circuit with a 0-10v Theatrical Lighting Dimmer

I'm trying to build a circuit which allows an Arduino to control 6 channels of lighting from an old Strand Act 6 Dimmer. These dimmers have 8-pin DIN connector on them like this specification. Pin 7 ...
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  • 201
6 votes
2 answers
1k views

PWM DAC Filter explanation

I found this design idea (Fast-settling-synchronous-PWM-DAC-filter-has-almost-no-ripple) on EDN where an RC integrator and a sample/hold amplifier are used to filter PWM signals into stable DC values. ...
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  • 475
5 votes
2 answers
2k views

Debugging an MCU short circuit

I have a board with an STM32F103VGT6 MCU. Yesterday, the MCU worked fine, I had just gotten semihosting working, LED blinking, played around getting a timer running and so on. I then decided to try ...
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3 votes
2 answers
2k views

Cascade DACs to get higher resolution

I got a RAM-DAC with 3 channels and 6 bits for each channel. The device in question seems very straightforward to use with a modern MPU like an AVR. The resolution is a bit low, so I thought about ...
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3 votes
2 answers
2k views

How to calculate resistor values for a VGA DAC

I have an FPGA and want it to drive a VGA monitor. I want more than 3 bits of color so I need a DAC of some sort. So I want to make a resistor dac. My plan is to have 3 bits per subcolor. So total of ...
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1 vote
2 answers
1k views

Audio Noise: ATMEGA328P, MCP4921, and LM386

I am trying to build a simple audio circuit. The goal is to store .wav files in the form of hex files in the ATMEGA328P's flash memory, and output the audio through a small speaker by using an ...
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0 votes
2 answers
4k views

How is SNR defined in a DAC?

In the datasheet of the dsPIC33FJ128GP802 it is said that the SNR of the 16 bit audio DAC module is 61 dB. What does this mean? How much RMS white noise voltage should I hope to see? I know the SNR ...
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0 votes
1 answer
128 views

A very basic question about DAC conversion in a sound card

This is a conceptual question about how a sound card converts digital data to analog. To illustrate this let's say we have constructed a discrete data which represents a sinusoid with particular ...
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5 votes
1 answer
793 views

How are DACs integrated in color LCD screens?

I'm having trouble imagining what actually happens inside an LCD screen. I picture digital RGB data for each pixel getting sent to the screen through a connector. Lets say we have 24-bit color for ...
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4 votes
2 answers
2k views

Stuck codes in samples from ADC

I am currently testing a 16-bit DAC and a 18-bit ADC. In many tests I have found the ADC to get "stuck" at codes, especially at the ends of the input range. Both the DAC and ADC operate in bipolar ...
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4 votes
2 answers
3k views

Units of noise spectral density

I'm reading the datasheet of a DAC (see page 6), and the "Output Noise Spectral Density" has units V / Hz^(1/2). The Wikipedia article on noise spectral density ...
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3 votes
5 answers
2k views

How to sample audio at Nyquist frequency with MSP430F5438?

I want to: Input an analog audio track Using the microcontroller ADC, convert it to a digital output Then have the microcontollers/boards timer sample the data at selected intervals Resample the "...
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3 votes
2 answers
426 views

What is the meaning of handling error in 1.5 bit ADC?

In the diagram shown bellow we have 1.5 bit ADC stage. We have Vin which is an analog signal and it could be translated as 00, 01...
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3 votes
1 answer
948 views

Why modern oscilloscopes use hardware triggering?

I've been learning how DSOs work for the past few days. As far as I understand, digital storage oscilloscopes have trigger circuitry, which usually consists of an analog comparator and a DAC. A ...
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3 votes
1 answer
704 views

Weird samples from SAR ADC

I am playing around with some SAR (Successive Approximation) A/D-converters. I have made a test circuit where I have a 16-bit DAC from Texas Instruments (R2R-based) and an 16-bit SAR ADC from Analog ...
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  • 295
3 votes
3 answers
2k views

How to build an arbitrary (one-shot) pulse generator?

I need a circuit/IC that can generate a single pulse with a variable pulse width (I would want a minimum of 50 ns but if that is not possible the next minimum can be 1 μs, and even if that is not ...
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2 votes
1 answer
122 views

Multiple lengths in DAC datasheet

The last page of this DAC datasheet gives dimensions of the chip: Some of these dimensions come is 3-tuples (such as the pin width: 0.30 | 0.37 | 0.45). What does ...
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2 votes
1 answer
110 views

Altering reference voltage of DAC

I'm making a circuit which requires an adjustable voltage gain (0 - 1). I thought of using a multiplying DAC (R-2R type) with input voltage connected to its Vref pin. The input code to the DAC shall ...
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  • 109
2 votes
4 answers
12k views

Convert a PWM to analogue with double the voltage range?

I have a PWM output (0-5v) that I need to convert to an analogue voltage. Simple = RC filter. However, the voltage range from that analogue voltage needs to be twice that of the input voltage, and I'm ...
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  • 1,042
2 votes
3 answers
674 views

why the quantised of DAC will affect the amplitude of the output waveform of AD 9850?

By referring to the http://www.analog.com/static/imported-files/data_sheets/AD9850.pdf, for page 9 and figure 5, why the quantized D/A converter affect the amplitude of the output waveform?
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  • 139
1 vote
1 answer
79 views

Which formula is correct for a Digital-Analog-Converter?

I am looking for the formula for an ideal DAC: a device that takes in a digital code and returns an analog value rfwireless-world.com claims $$V_{out} = D\cdot V_{ref}/(2^N-1)$$ where D is the ...
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1 vote
1 answer
971 views

Synchronize internal DAC to I2S on STM32F4

I have a CS4344 DAC connected to my STM32F407 outputting sound at a 44.1kHz rate with DMA and I2S and I would like to output and envelope signal through the internal DAC of the STM32F4, in sync with ...
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1 vote
1 answer
67 views

How to simulate this circuit for common mode voltage effect?

Regarding my previous question and this paper, I wanted to simulate the circuit below to see whether it is rejecting common mode voltage as claimed. The paper says that sharing DAC's Vref with non-...
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  • 402
1 vote
1 answer
141 views

DAC-driven Variable Voltage Power Supply using MOSFETs

I'm trying to achieve a variable voltage supply where the voltage can be tuned by a DAC. The DAC is limited to ~3.3 V, but the design goal for the resulting voltage supply is V_out between 0 and 15 V ...
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  • 133
1 vote
1 answer
473 views

ESP32 DAC cannot output zero volts

I made a circuit to use with my ESP32 to test 18650 battery capacity. During tests I didn't notice that when I do dacWrite(dacpin, 0); output on DAC pin gets 0.1V ...
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  • 478
1 vote
2 answers
986 views

DAC controlled LDO as current source

Currently I use a LT3083 as a constant current source more or less according to the datasheet as given in the first image. Instead of a single set resistor however is use a fixed resistor in series ...
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  • 153
0 votes
2 answers
2k views

DAC to run a 555 Timer [duplicate]

I am trying to create a PWM signal using a POT from 555 Timer to control speed of a 5V DC motor. I have a development board with a C8051F020 microcontroller, a 100K POT and an LCD display. The ...
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  • 1,455
0 votes
1 answer
47 views

How do LDMOS datasheets label current draw through the gate?

I'm trying to figure out how much current is required to bias a FET's Vgs so I can choose a DAC to set the gain. If I understand correctly, very little is required, but I couldn't find something ...
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0 votes
1 answer
382 views

How to make desired waveforms by AD5668?

In another thread I asked about making sawtooth wave form via harmonics ( Here ) and someone suggested using AD5668 (octal DAC ). I looked at its datasheet but couldn't understand how it can make a ...
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0 votes
2 answers
221 views

I need diodes to build a R-2R ladder DAC from original TTL chips (not Arduino) don't I?

I am thinking through how I could turn my analog oscilloscope with X-Y mode and Z input in the back into a simple computer monitor. I am learning about generating a proper sawtooth with a constant ...
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0 votes
5 answers
3k views

Convert PWM to Analog using a DAC chip in order to emulate a Potentiometer for audio

I'm trying to control audio level/gain (from line or amplified signal) using an Arduino. I do not want to use SPI, for this project I can only use the PWM outputs, thus I do not want to use a digital ...
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