fogandflower
Newbie level 5
Hi, I have two issues in 6bit DAC test. The clock frequency is 3.5G, data rate is 440M.
1) DAC output use source follower as driver, the design is differential output expect 200mv Vp-p, however the test result only 60mv-35mv. When we use high-Z probe to measure, the source follower gate swing is about 220mv. My question is, in what condition, the source follower output swing was limited?
2) When we check the spectrum, we can find two spur very near the signal like mirror image, the delta f is 145Khz, and amplitude is -49dBc, the spur follow the input signal no matter in low frequecy (10M) or high frequency (880M) with constant delta f. I really clueless about this two mirror spur. Please help!
1) DAC output use source follower as driver, the design is differential output expect 200mv Vp-p, however the test result only 60mv-35mv. When we use high-Z probe to measure, the source follower gate swing is about 220mv. My question is, in what condition, the source follower output swing was limited?
2) When we check the spectrum, we can find two spur very near the signal like mirror image, the delta f is 145Khz, and amplitude is -49dBc, the spur follow the input signal no matter in low frequecy (10M) or high frequency (880M) with constant delta f. I really clueless about this two mirror spur. Please help!
