X9312APPLICATIONS INFORMATION Electronic digitally controlled (XDCP) potentiometers provide three powerful application advantages; (1) the variability and reliability of a solid-state potentiometer, (2) the flexibility of computer-based digital controls, and (3) the retentivity of nonvolatile memory used for the storage of multiple potentiometer settings or data. Basic Configurations of Electronic Potentiometers V V R R VH VW/RW VL I Three terminal potentiometer; Two terminal variable resistor; variable voltage divider variable current Basic CircuitsBuffered Reference VoltageCascading TechniquesNoninverting Amplifier R1 +V +V +5V +V V LM308A S + +5V VO – VW OP-07 + VREF –5V V X OUT V – W/RW +V R2 -5V R1 V V OUT = VW/RW W/RW (a) (b) VO = (1+R2/R1)VS Voltage RegulatorOffset Voltage AdjustmentComparator with Hysteresis R R 1 2 V V LT311A IN 317 O (REG) VS V – S V R O 1 100kΩ + – VO + Iadj TL072 } } R2 10kΩ R R 1 2 10kΩ 10kΩ VUL = {R1/(R1+R2)} VO(max) VO (REG) = 1.25V (1+R2/R1)+Iadj R2 VLL = {R1/(R1+R2)} VO(min) +12V -12V (for additional circuits see AN115) 7 FN8176.0 March 15, 2005
