+/-15V power supply using LM317 and LM337 regulator ICs     How to designa /-15V power supply using LM317 and LM337 regulator ICs. Thx The voltage is used to DAC (AD669) I have try to design the circuit.... Is it Right?? 發表人 - cyw1984 於 2005/09/28 22:12:28

EXTERNAL CAPACITORS An input bypass capacitor is recommended. A 0.1uF disc or 1uF solid tantalum on the input is suitable input bypassing for almost all applications. The device is more sensitive to the absence of input bypassing when adjustment or output capacitors are used but the above values will eliminate the possibility of problems. The adjustment terminal can be bypassed to ground on the LM117 to improve ripple rejection. This bypass capacitor prevents ripple from being amplified as the output voltage is increased. With a 10uF bypass capacitor 80dB ripple rejection is obtainable at any output level. Increases over 10uF do not appreciably improve the ripple rejection at frequencies above 120Hz. If the bypass capacitor is used, it is sometimes necessary to include protection diodes to prevent the capacitor from discharging through internal low current paths and damaging the device. In general, the best type of capacitors to use is solid tantalum. Solid tantalum capacitors have low impedance even at high frequencies. Depending upon capacitor construction, it takes about 25uF in aluminum electrolytic to equal 1uF solid tantalum at high frequencies. Ceramic capacitors are also good at high frequencies; but some types have a large decrease in capacitance at frequencies around 0.5MHz. For this reason, 0.01uF disc may seem to work better than a 0.1uF disc as a bypass. 以上是製造廠建議. 15V : R1=2.2K,R2=220歐姆 , 值會有些許差異, 如必要可以串聯電阻來達到15V Vo差不多= 1.25*[1 (R1/R2)] ==>近似值 建議不要用VR , 那不是穩定的東西,久了會變 , 原設計圖VR 旁可以並電容,值約 10 - 68uf , 原廠建議10uf , 小弟試過47uF 在 Audio 部分效果不錯,供參考.