The usual schematic of a state-variable filter with two inverting integrators is well known. Curiously, the input signal is almost always connected to the minus input of U1. Figure 1 is an example ...

Until the advent of FM, combiners were rarely required. After FM was introduced, the need for a method of feeding two or more FM frequencies into a single FM antenna developed. AM operation had ...

Almost every engineer has had the opportunity to top off his or her vehicle’s air conditioner with a can or two of R131A refrigerant. But don’t throw the empty can away — with a little work, you can ...