Abstract: This design idea describes a simple circuit to generate a programmable negative control voltage. It takes the output of a single supply digital-to-analog converter (DAC) and produces a variable negative voltage. The DAC output from 0V to +2.5V is converted to 0V to -5V at the output. Early digital-to-analog converters (DACs) were designed with standard R-2R ladders, and produced a negative output voltage. These early DACs (such as the MX7837/MX7847 and MAX523) require both a positive and a negative supply rail to accommodate their negative output. With the transition to single-supply integrated circuits, however, many modern DACs now operate with a single supply rail and an inverted R-2R ladder. The inverted R-2R ladder produces a positive output voltage. Despite the popularity of single-supply ICs, some applications still require a negative control voltage. One solution for this purpose is a modern, inverted R-2R ladder DAC and op amp (Figure 1). When compared with older DACs containing standard R-2R ladders, this approach offers lower supply voltages, higher speed, and smaller packages. Figure 1. This compact circuit enables microcontroller IC2 to generate a variable negative voltage. The DAC (IC3), operating with a 2.5V applied reference voltage from IC1 and driven by microcontroller IC2, produces an output swing from 0V to 2.5V. Op amp IC4 inverts and amplifies this output to produce a 0V to -5V output. For test purposes, a software routine enables the microcontroller to generate a 0V to -5V triangle-wave output. Please note that the output impedance of the DAC (IC3) is 6.25kΩ ±20%. To eliminate system gain errors that are caused by the DAC's output impedance, buffer the DAC output before the IC4 inverting stage. A similar version of this article appeared in the December 6, 2001 issue of EDN magazine. 관련 부품   APP 1074: May 24, 2002 MAX4162 SOT23, 마이크로파워, 단일 전원, Rail-to-Rail I/O Op 앰프 전체 데이터 시트 (PDF, 304kB) 무료 샘플 MAX541 +5V, 직렬 입력, 전압-출력 16비트 DAC 전체 데이터 시트 (PDF, 248kB) 무료 샘플 MAX542 +5V, 직렬 입력, 전압-출력 16비트 DAC 전체 데이터 시트 (PDF, 248kB) 무료 샘플 MAX837 4핀 마이크로파워 전압 모니터 전체 데이터 시트 (PDF, 108kB) 무료 샘플 자동 업데이트 관심 분야의 애플리케이션 노트가 나올 때 자동으로 업데이트를 원하십니까? 그렇다면 EE-Mail™을 신청하십시오. We Want Your Feedback! 의견을 보내주세요! 위 내용이 도움이 되셨나요? 여러분의 의견을 기다립니다 — Maxim은 보내주신 정정이나 제안사항을 반영하고 있습니다. 이 페이지를 평가하고 의견을 보내주십시오.   다운로드, PDF 형식 (29kB)  AN1074, AN 1074, APP1074, Appnote1074, Appnote 1074