Introduction Occasionally， we are tasked with designing circuitry for a specific purpose. The request may have customer origins or it may be an in-house requirement. Alternately， a circuit may be developed because its possibility is simply too attractive to ignore1. Over time， these circuits accumulate， encompassing a wide and useful body of proven capabilities. They also represent substantial effort. These considerations make publication an almost obligatory proposition and， as such， a group of circuits is presented here. This is not the first time we have displayed such wares and， given the encouraging reader response， it will not be the last2. Eighteen circuits are included in this latest effort， roughly arranged in the categories given in this publication’s title. They appear at the next paragraph.

　　Voltage Controlled Current Source—Ground Referred Input and Output A voltage controlled current source with ground referred input and output is difficult to achieve. Executions exist， but are often cumbersome， involving numerous components. Figure 1’s conceptual design utilizes a differential amplifier featuring differential， uncommitted feedback inputs. The independent feedback inputs permit the differential signal inputs to operate anywhere inside their common mode range， unencumbered by feedback interaction. Similarly， the differential feedback ports may sense referred to any point within their common mode range. In both cases， common mode range extends from V– to within 2V of the positive rail. Output swing extends to both rails.

　　圖1.概念接地電壓控制雙極電流源采用差分放大器的分離反饋輸入。遵守限制是由供應電壓，輸出電流容量和輸入共模范圍。