No, you can use a fast external comparator on the sin output. The problem with AD9851 is the onchip comparator. It has a large jittter, that's why the performance of square wave degrades. Also at 50MHz with an unknown load, a buffer is needed anyway on both sin and square otputs. AD9851 is a good product, I use it in a lot of applications. You have to understand only how the Nyquist is affecting the SFDR and to design a proper elliptical filter. Vasile On Mon, Oct 12, 2015 at 8:38 PM, David C Brown wrote: > AD are talking about the chip. The way the chip is integrated into the > module might affect the square wave performance. It would be very unusua= l > for a vendor to understate the performance of his product. > > On 12 October 2015 at 17:20, Bob Blick wrote: > > > That's not what Analog Devices says. They quote 33% of the reference > > clock (up to 125MHz, which is what I see on the eBay modules). So that'= s > > 40MHz right there. Really not trying to lead you down a blind alley. > > > > Cheers, Bob > > > > On Sun, Oct 11, 2015, at 11:22 PM, David C Brown wrote: > > > The AD9850 sine wave generators are just that - sine wave generators. > > > They > > > quote a square wave up to 5MHz which is not good enough. > > > > > > On 12 October 2015 at 03:33, Bob Blick wrote: > > > > > > > Hi David, > > > > > > > > Have you looked the plethora of AD9850 DDS sinewave generators? The= y > > > > have a comparator for squarewave output. I don't know what your spe= c > > is, > > > > but you could put a toggling flip-flop on the comparator output if > you > > > > need better duty cycle accuracy than the comparator itself (if you > can > > > > lose the upper octave). > > > > > > > > Best regards, Bob > > > > > > > > On Sun, Oct 11, 2015, at 11:04 AM, David C Brown wrote: > > > > > I am looking for a module to generate logic level square wave up = to > > at > > > > > least 20MHz (50 would be better) within a $100 budget. There are= a > > > > > number > > > > > of items on eBay but none have them seem to have a proper spec. > Any > > > > > recommendations from experience? > > > > > > > > > > -- > > > > > __________________________________________ > > > > > David C Brown > > > > > 43 Bings Road > > > > > Whaley Bridge > > > > > High Peak Phone: 01663 733236 > > > > > Derbyshire eMail: dcb.home@gmail.com > > > > > SK23 7ND web: www.bings-knowle.co.uk/dcb > > > > > > > > > -- > > http://www.fastmail.com - Access all of your messages and folders > > wherever you are > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > -- > __________________________________________ > David C Brown > 43 Bings Road > Whaley Bridge > High Peak Phone: 01663 733236 > Derbyshire eMail: dcb.home@gmail.com > SK23 7ND web: www.bings-knowle.co.uk/dcb > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .