Abstract: Two integrated circuits (ICs) and some associated components form a voltage-controlled sawtooth generator that costs less than $3 and produces an auxiliary square wave at the same frequency. The generator is useful in a variety of applications. Its sawtooth waveform is commonly used, for example, to sweep the frequency of another generator. Two ICs and some associated components (Figure 1) form a voltage-controlled sawtooth generator that costs less than $3 and produces an auxiliary square wave at the same frequency. The generator is useful in a variety of applications. Its sawtooth waveform is commonly used, for example, to sweep the frequency of another generator. Figure 1. This simple voltage-controlled sawtooth-waveform generator operates with a linearity of 1% or less. A second output provides a square wave of the same frequency. IC1 with Q1 and R1 forms a voltage-controlled current source. Current I0 discharges C1 until the C1 voltage is less than 1.66V, which trips the IC2A comparator and swings its output to 5V. Current through the diode-connected transistor (Q2) charges C1 until its voltage reaches 3.33V, causing the IC2A output to swing back to ground. This repeating cycle determines the output frequency: fOUT = (3(5V +VC)/5V)(1/R1C1). The maximum fOUT occurs when VC = 1.66V, but fOUT can be set as high as desired by adjusting the values of R1 and C1, subject to the limitations of comparator IC2A's slew rate and settling time. The MAX991 (as IC2A) yields a rise time of 150ns when a 3300pF load (C1) is present at its output. Lower C1 values yield shorter rise times, which allow higher fOUT. When fOUT approaches its maximum, the finite tr degrades the VCO linearity somewhat. By careful selection of R1 and C1, this effect will be minimized and linearities of 1% or better can be achieved. The generator's linearity determines the frequency range over which it can operate. This generator's good linearity performance allows it to operate across several decades of frequency. A similar version of this article appeared in the July 26, 1999 issue of Electronic Design 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 825: Oct 16, 2001 MAX4162 SOT23, 마이크로파워, 단일 전원, Rail-to-Rail I/O Op 앰프 전체 데이터 시트 (PDF, 400kB) 무료 샘플 MAX991 고속, 마이크로파워, 저전압, SOT23, Rail-to-Rail I/O 비교기 전체 데이터 시트 (PDF, 332kB) 무료 샘플   다운로드, PDF 형식 (33kB)  AN825, AN 825, APP825, Appnote825, Appnote 825