would you be willing to share some thoughts as to why you’re making that change and what the tradeoffs are? I’m guessing you’re beating the cost of a 1251 by a wide margin, but i am a bit surprised to see you use it for everything like this.
Oh, there are tons of advantages to using the LT1251/LT1256. The biggest cost saver is that if you’re using accurate voltage reference circuits, you don’t need any trimmers!! They are laser calibrated in the factory. Trimmers easily can cost $1-$2 each even in quantity, for a nice quality sealed option, and then add another dollar of tech labor, and discrete options with the same performance can quickly match the cost of LT1251/LT1256. Another advantage on the DFM side is much lower component counts. On the design side of things, it’s dead simple and always works, too – whereas more complex discrete circuitry can end up requiring more revision cycles. In 2015 as we launched into Expedition series development it was very important to expand the product line quickly, so LT1251/LT1256 has been a life saver in this regard.
That said, now that we have stabilized and can afford longer R&D and revision cycles, we’re very interested in optimizing the product line as a whole, for testability, performance, and consistency in manufacturing. Not that we have a lot of problems to solve – we just want to continue doing the best job possible. Since most purchasing is done for the product line rather than an individual product, we’re able to hit some quantity breaks we were not able to before (whereas LT1256 qty pricing ends up capping out around 100 pieces.) So we’re auditioning some discrete circuits now, and also have the kind of test gear we need to do some more advanced signal integrity testing of all the modules.
With active attenuverters and signal paths (like using analog switch ICs controlled by mechanical switches) there are numerous signal integrity advantages. One of them is that the control pot voltage can be manipulated to fine tune the range and slope of a control in the way putting the video through a pot directly cannot. For example, in our active attenuverter circuit there is a deadband region in the center, so you can reach a nulling point easier.