A direct digital synthesizer (DDS) creates waveforms from a single frequency reference clock. Typically the reference frequency is fed into a numerically controlled oscillator (NCO) that controls the final frequency and waveform type from where the quantized digital data is converted to analog using ...

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48 views

Review and question about AD9838 circuit

I have tried to come up with a schematic of using AD9838. I used the eval. board schematic and modified it to my needs. The eval. board schematic can be found on page 9 here: AD9838 eval. board ...
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1answer
126 views

opamp circuit for amplify up from 1.1V to 5 V

I am doing a DDS function generator with AD 9850 ,because of the charactericts of DAC converter http://www.analog.com/static/imported-files/data_sheets/AD9850.pdf, page 9 figure 5, the output of ...
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3answers
107 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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1answer
156 views

Strange noise on DDS

I have built an FPGA based DDS (fc=200MHz. out: 0-50 or 0-80 MHz) . I have a decent DAC output wave and now trying to build an appropriate filter for it ( Fig-1 ). The filter works rather fine but ...
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2answers
89 views

High speed counter with step control

I am trying to build my own DDS. I want to make a lookup table (eeprom)that controls steps of a counter and then feed it into a DAC to make a wave form ( something like that Direct Digital ...
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2answers
294 views

Why does my wave signal from AD9850 / AD9851 DDS get cut off?

I have the AD9850 and AD9851 version of this board. I have written the necessary code to interface these with my microcontroller. However, when I sample the sine output signal from the DDS it gets ...
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1answer
131 views

How to identify counterfeit Analog Device products?

Recently I bought two AD9850 DDSs from a friend ( I think he had bought them from his home country).They worked just for minutes! After hours challenging with them, I thought problem is because of my ...
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1answer
153 views

Why AD834+AD811 voltage controlled amplifier does not accept around ground signals?

I have setup a circuit according to page 15 of AD811 Op-Amp datasheet . The design receives 0.5-1.2 vpp sine wave between 1Hz-50MHz from AD9850 DDS and it also has around +0.7 to +1 v offset voltage. ...
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1answer
138 views

AD9850 comparator problem. How to calculate is frequency?

I want to convert a sine wave produced from AD9850 (opens *.pdf) into square wave with its inbuilt comparator. AD9850 has a fast comparator with 3ns rise/fall time and propagation delay= 5.5ns. ...
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2answers
236 views

How to protect a signal from output short circuit?

I have made a signal generator based on DDS and amplified its output to 0-20 V pk-pk. Now I want to prepare the output side. My main concern is short circuit protection to prevent damage to my device. ...
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1answer
95 views

What is optimum maximum frequency of DDS?

According to most DDS datasheets, they can produce up to half the maximum frequency. for example for AD9850, max clock is 125 MHz and it can produce up to 62.5 MHz. But in higher frequencies, the ...
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1answer
86 views

AD9850 just works for a few minutes?

I am trying to drive AD9850 (DDS). First I started with a module , programmed the micro (ATMega128 ) and everything was ok ( It means there may not be a software error). Then I decided to make my own ...
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1answer
160 views

which one is better for smoothing a sine wave: Low pass filters or a serially connected inductor?

Smoothing a sine wave is my main concern in this question. I have a sine wave made by DDS that in higher frequencies shows some steps. Normally in every electronic class it is heard that the best ...
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2answers
157 views

Wave form distortion in AD9833

When using AD9850, I can see a very clean and smooth sine wave but this is not the case by AD9833. In AD9833 multiple steps are visible in the output that gets worse in higher frequencies( > 2MHz) ...
2
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1answer
191 views

What is output amplitude of Direct Digital Sythesizers as AD9850?

By looking at AD9850 DDS or other similar parts made by Analog Devices Company it is obvious that the output signal amplitude changes by frequency. This can be shown as x= pi* fout / fClock and ...
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1answer
446 views

AD9850 and other DDSs: How to stabilize output gain after low pass filtering?

Recently I got familiar with DDS family of ICs. They are fine and nice to work with but there is a problem with them: The output made by DAC has harmonics that according to the datasheet they need to ...
2
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2answers
664 views

Sawtooth/ramp waves with fixed amplitude from sine or square clock source?

I hope someone can help me out! A bit of background info: I have created a DDS based signal generator (Using PIC MCU to drive a AD9833 for DDS output). The generator is capable to produce sine, ...
6
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1answer
388 views

LC filter vs Isolation tranformer for AC coupling of a DAC output

I'm trying to decide between a few choices for coupling the output DAC of a DDS with the rest of my circuit. DDS dac's I'm looking at are typically either single-ended or have complimentary current ...
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2answers
263 views

How good are commercial DDS IC's for low frequency applications?

I'm making a precise, low-current current source for a bio-impedance meter using a howland current pump. Currently the current pump is driven by a wien-bridge oscillator to produce a 1V p-p 100hz ...
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1answer
519 views

Generate sine wave in VHDL, with the use of 10-bits DAC [closed]

I want to generate a sine wave with 20Mhz frequency, using a FPGA (Cyclone 3 EP3C10E) and an external 10bit DAC converter (http://www.analog.com/static/imported-files/data_sheets/AD7533.pdf). I have ...
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1answer
96 views

Xilinx DDS IP for modulating a carrier

I explored XIlinx IP for DDS, and am able to get 2 different frequencies (samples) based on the input clock. But what I want is to frequency modulate the clock itself. So basically when I say I ...
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2answers
189 views

UHF Phase Modulation

I would like to design a system that produces -10 degrees and +10 degrees phase shifts at 409.6MHz (Basically BPSK). The way I'm thinking about approaching this is by using a DDS to generate the BPSK ...
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1answer
314 views

Simple Implementation of the AD9834 DDS Chip [closed]

I'd like to see a simple implementation of the AD9834 DDS chip. I'd like to use this in a homebrew Amateur Radio build. The test circuits in the datasheet were rather confusing, and the ...
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3answers
3k views

Driving 50W-250W ultrasonic transducers with sine: Any Class B 135KHz monolithic power amp ICs?

My project needs to drive a medium power ultrasonic piezoelectric transducer from a sine wave (/ sawtooth) sweep generator that sweeps +/- 2% of the transducer resonant frequency. The question: What ...
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2answers
314 views

Generating various emission modes via DDS

I know it is common to generate sine waves via Direct Digital Synthesis (DDS). What I would like to know is if it is possible to generate a modulated signal via DDS and if so what would be a practical ...
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2answers
485 views

What kind of effects does a relay have on signals?

Currently I'm working on a DDS based function generator. The idea is to use an AD9834 chip that will generate a triangle/sine or square wave. With some amplification electronics I want a configurable ...