By adding a JFET in cascode with a linear regulator (see the figure below), you can extend the regulator's input-voltage range. The regulator shown suits battery-powered applications, because its CMOS circuitry draws only 12µA maximum, regardless of the output-current level. The chip's VIN limit of 16.5V excludes some applications, however. Connecting the external JFET extends the circuit's input-voltage limit to the JFET's gate-source breakdown voltage. A J106 device, for instance, extends this limit to 25V. The J106 has a 6-ohm on-resistance, and IC1 has a minimum VIN/VOUT differential of 0.6V to 0.8V; thus, for low load currents, the combination can deliver a 5V output with chip inputs as low as 5.6V. The circuit can deliver 40mA at 5V with a 6.5V VIN. Replacing the J106 with a 2N4391 JFET increases the allowable input voltage to 40V. The 2N4391 has a 30-ohm on-resistance, so it delivers 40mA with a 2V in/out differential or 10mA with a 1V differential. Figure 1. Adding a JFET in cascode with a linear-regulator IC extends the allowable input voltage to 25V or 40V, depending on the JFET device used. A similar version of this article appeared in the July 12, 1990 issue of Electronic Design. 관련 부품   APP 482: Dec 01, 2000 MAX666 듀얼 Mode™ 5V 프로그래밍 가능한 마이크로파워 전압 레귤레이터 전체 데이터 시트 (PDF, 376kB) 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 (23kB)  AN482, AN 482, APP482, Appnote482, Appnote 482