Abstract: This article shows an example of implementing a 4-20mA or 0-20mA current-loop output using a voltage output digital-to-analog converter (DAC) and a V to I converter. Current-loop signals, as opposed to voltage signals, are commonly used in industrial systems because they are much less subject to noise and relatively indifferent to line length (because the current is unaffected by line resistance). The circuit of Figure 1 allows digital selection between the two standard ranges of current-loop transmission common in industrial systems (0-20mA and 4-20mA). Figure 1. This circuit's single control input selects a current-loop range of 0-20mA or 4-20mA. The analog switch (IC2) controls a resistive divider driven by the 2.5V reference (IC1), such that the AGND offset is either 0V or 0.4V, and the DAC's Δ voltage (OUT minus AGND) is either 2V or 1.6V. Thus, for 0mA to 20mA, Δ = 2V and AGND = 0V; for 4mA to 20mA, Δ = 1.6V and AGND = 0.4V. The voltage-output D/A converter (IC3) drives a V/I converter (op amp IC4 and associated resistors) to produce the current loop. Because the DAC's output resistance in voltage mode is high (11kΩ), the resistor values are are made large to preserve accuracy. The op amp's output-drive capability is 80mA. To maintain good linearity, the reference voltage at OUT (IC3 pin 1) should not exceed 2V. A similar version of this article appeared in the October 15, 2001 issue of EE Times magazine. 의견을 보내주세요! 위 내용이 도움이 되셨나요? 여러분의 의견을 기다립니다 — Maxim은 보내주신 정정이나 제안사항을 반영하고 있습니다. 이 페이지를 평가하고 의견을 보내주십시오. 자동 업데이트 관심있는 분야의 애플리케이션 노트가 나올 때 자동으로 업데이트 받고 싶으세요? 그렇다면 EE-Mail™을 신청하십시오. 추가 정보   APP 1085: May 31, 2002 MAX4165 셧다운 기능이 내장된 고출력 구동, 정밀, 저전력, 단일 전원, Rail-to-Rail I/O Op 앰프 전체 데이터 시트 (PDF, 1.2MB) 무료 샘플 MAX4543 저전압, 단일 전원, 듀얼, SPST/SPDT 아날로그 스위치 전체 데이터 시트 (PDF, 252kB) 무료 샘플 MAX551 10핀 µMAX 패키지로 제공되는 +3V/+5V, 12비트, 직렬, 멀티플라잉 DAC 전체 데이터 시트 (PDF, 176kB) 무료 샘플 MAX6125 SOT23, 저가, 저전압강하, 3단자 기준 전압 전체 데이터 시트 (PDF, 728kB) 무료 샘플   다운로드, PDF 형식 (34kB)  AN1085, AN 1085, APP1085, Appnote1085, Appnote 1085