LTC6409
Recommended for New Designs
The LTC6409 is a very high speed, low distortion, differential amplifier. Its input common mode range includes ground, so that a ground-referenced input...
LTC6409 on Analog.com
Hello
I want to use ADA4930 as an ADC driver in dc-coupled and single ended topology.
the gain is 0.5V/V and the source is 2Vpp and 50 Ohm. (Rf=301 Rg=294 Rt=56.9)
but the source has a little output offset. (some mV maximum)
I've studied in the Analog devices's application notes that I should apply some equal DC voltage at the inputs of the FDA.
I can not measure the output offset very accurate.
how should I provide this voltage and apply it at the second input of the FDA?!!!
please reply me as fast as you can. I don't have enough time.
Best Regards
Hi again Ali,
What you could do is to have an ac-coupled inputs to reject the DC offset. Also, the best way for you realize that is thru DiffAmp Calc software, which you could download here. http://www.analog.com/en/design-center/interactive-design-tools/adi-diffampcalc.html
Should you additional questions, just let me know.
Regards,
Jino
Hi Ali,
I missed that. Apologies.
Anyway, here are the things that you can do. Refer to the figures below.
1. Set the ADA4930 at Differential Input topology. Set dc offset and input voltage of the Inverting Input at zero. See example below.
2. Apply some voltage at the Vs dc on the Non-Inverting Input, Vp. As you watch closely, the output sinewaves move with respect from each other. The offset is the difference between the waveforms centerline divided by the gain. In the example below, I set it to 0.4 V so that makes the outputs swing at 200 mV from each other. See below.
In your case, you have to observe that voltage difference in each output, an oscilloscope graph would suffice.
3. You must correct the offset by applying an equal voltage on the Vs dc of the Inverting Input, Vn. See below.
Observe as the two output voltages center around Vocm.
I hope this helps.
Regards,
Jino
