Voltage Regulator

A voltage regulator is a device which takes an input voltage and outputs a stable fixed voltage


1.齊納二極體 (Zener Diode)

• 1.12V-->5V (Select a proper Zener Diode voltage)
• 2.最小輸入電壓須比輸出的穏壓大2V以上

2.Fixed voltage regulators

• 1.LM7805 ==> 5V; LM7812==> 12V
• 2.最小輸入電壓須比輸出的穏壓大2V以上

3.Adjustable output voltage

• max allowed IN/OUT voltage difference which is 40v
• OUT = 1.25*(1+R2/R1)
• 

4.參考電壓IC : LM385 , AD580

那如何做5V--> 3.3V ? or 3.3v --> 1.8v

• 使用線性穩壓器 LDO (Low Dropout) , 只需要差到0.5V以上
• LM2940, LM2941
• LM317

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