| Electronics > Beginners |
| Op amp not working out as planned |
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| netdudeuk:
The AD9833 has a VOUT Maximum of 0.65V and a VOUT Minimum of 38mV. So, that's the peak input voltage. Regarding the peak output voltage, here are the specifications for a branded budget 5MHz arbitrary function generator - 2mVpp~10Vpp (50?, ?10MHz) 4mVpp~20Vpp (high impedance, ?10MHz) So, maybe something along these lines (Vpp and maximum frequency) looks sensible for my purpose, which is to have a signal generator to experiment with op amps (which I'm now actually doing), filters, etc ? I'll not be putting the signal down long cables. I understand that I'm going to have to put in more volts in if I want more volts out. Thanks |
| StillTrying:
--- Quote from: netdudeuk on April 05, 2018, 11:10:47 am ---The AD9833 has a VOUT Maximum of 0.65V and a VOUT Minimum of 38mV. --- End quote --- Yep, it outputs a constant amplitude sine, triangle or square. But with only 25M samples per second I think any wave over 1MHz is going to be quite rough, and 12.5MHz not really possible other than just a 12.5MHz square, unless I've missed something! http://www.analog.com/media/en/technical-documentation/data-sheets/AD9833.pdf Have you scoped the AD933's 38-650mV output directly to see what a ~1MHz+ sine, triangle and square look like? I wouldn't know where to go from here in producing a variable amplitude, variable offset output, but you could get the AD9833's output to a 0V centered 1.25Vpp with something like this. |
| Zero999:
--- Quote from: StillTrying on April 05, 2018, 07:40:58 pm --- --- Quote from: netdudeuk on April 05, 2018, 11:10:47 am ---The AD9833 has a VOUT Maximum of 0.65V and a VOUT Minimum of 38mV. --- End quote --- Yep, it outputs a constant amplitude sine, triangle or square. But with only 25M samples per second I think any wave over 1MHz is going to be quite rough, and 12.5MHz not really possible other than just a 12.5MHz square, unless I've missed something! http://www.analog.com/media/en/technical-documentation/data-sheets/AD9833.pdf --- End quote --- Yes you have missed something: an anti-aliasing filter will theoretically give a pure sine wave, right up to half the sampling frequency. In practise, you'll probably be limited to less than half the sample rate, but it should be possible to get a much higher frequency, than 1MHz and still have a decent sine wave. The problem will be the triangle wave and other arbitrary wave shapes, assuming this IC can do that, but I haven't chekted the data sheet. |
| StillTrying:
"The problem will be the triangle wave and other arbitrary wave shapes" It only does fixed amplitude 10 bit sine, triangle, and square, with a 28 bit word to set the frequency. I love the way the data sheet keeps saying "No other components necessary". :-DD |
| james_s:
At least to start with use a bipolar supply, you can work on making a single rail version after you have it working properly. Even a pair of 9V batteries can work quite well, op-amps typically draw very little current so you should be able to run it for a long time. Building a simple bench supply is another classic beginner project, it's hard to have too many power supplies. |
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