Tagged Questions

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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3
votes
2answers
60 views

Replacing Crystal Oscillator with DDS.

In a circuit like this, can the crystal oscillator be replaced with a DDS such as a AD9850? If so can it just be dropped in or would other components have to be changed? Second question, how ...
0
votes
1answer
65 views

Lowpass filter design with transimpedance and difference amplifiers

I have a DDS chip with complementary current outputs that I need to filter. I'm using a design like this: I need a different cutoff frequency, however - 2MHz instead of 50KHz. Note that I'm not ...
2
votes
2answers
198 views

Can an oscilloscope add a frequency component to my signal?

I want to check the spectrum of a DDS signal ("pure" sinewave) for undesired frequency components. The way I am doing it is by storing the waveform from a 2GS/s oscilloscope (Agilent DSO81204) and ...
0
votes
0answers
113 views

PIC16C54 used as signal generator from 100 KHz to 180 MHz

I have a PIC16C54 used as a DDS which generates 100 KHz to 180 MHz sine waves, model #80-035 datakit , I need source code but company is out of business. I purchased this as the early model called ...
1
vote
2answers
248 views

AD9850 can generate others waveform beside sine wave?

As know that AD9850 chip module can generate sine waveform, but does it can generate others waveform? as data sheet of AD9850 didnt mention it
1
vote
1answer
410 views

Can I use ATmega328 TX/RX pins to drive an R2R network and still use the serial port to program the MCU?

Background I wanted to make a simple function generator with an ATmega328 and an R2R resistor network, similar to Jesper Hansen's Mini DDS (Direct Digital Synthesis). To make the function generation ...
1
vote
1answer
108 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 ...
1
vote
1answer
197 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 ...
2
votes
3answers
186 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?
1
vote
1answer
201 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 ...
0
votes
2answers
116 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 ...
0
votes
2answers
441 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 ...
-1
votes
1answer
190 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 ...
1
vote
1answer
223 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. ...
0
votes
1answer
214 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. ...
2
votes
2answers
428 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. ...
0
votes
1answer
162 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 ...
2
votes
1answer
165 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 ...
0
votes
1answer
310 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 ...
1
vote
2answers
293 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
votes
1answer
275 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 ...
1
vote
1answer
821 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
votes
2answers
1k 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
votes
1answer
489 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 ...
1
vote
2answers
458 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 ...
-2
votes
1answer
974 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 ...
-2
votes
1answer
140 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 ...
3
votes
2answers
262 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 ...
-2
votes
1answer
437 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 ...
10
votes
4answers
5k 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 ...
1
vote
2answers
403 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 ...
4
votes
2answers
563 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 ...