* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Diode Characteristics
Survey
Document related concepts
Operational amplifier wikipedia , lookup
Schmitt trigger wikipedia , lookup
Josephson voltage standard wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Power electronics wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Charlieplexing wikipedia , lookup
Voltage regulator wikipedia , lookup
Power MOSFET wikipedia , lookup
Current source wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Rectiverter wikipedia , lookup
Current mirror wikipedia , lookup
Surge protector wikipedia , lookup
Laser diode wikipedia , lookup
Transcript
PN-Junction Diode Characteristics Forward Bias --- External battery makes the Anode more positive than the Cathode --- Current flows in the direction of the arrow in the symbol. Reverse Bias --- External battery makes the Cathode more positive than the Anode --- A tiny current flows opposite to the arrow in the symbol. Graphical PN-Junction Diode V-I Characteristic Forward Bias Region Reverse Bias Region Reverse breakdown Mathematical Approximation ID =Is (e VD ηVT -1) Ideal PN Junction Diode V-I Characteristic Forward Bias – Short Circuit Reverse Bias – Open Circuit Diode Reverse Recovery Time ta is the time to remove the charge stored in the depletion region of the junction tb is the time to remove the charge stored in the bulk semiconductor material Reverse Recovery Characteristics Soft Recovery Reverse recovery time = trr = ta+tb Peak Reverse Current = IRR = ta(di/dt) Reverse Recovery Characteristics Abrupt Recovery Reverse recovery time = trr = ta+tb Peak Reverse Current = IRR = ta(di/dt) Series-Connected Diodes • Use 2 diodes in series to withstand higher reverse breakdown voltage. • Both diodes conduct the same reverse saturation current, Is. Diode Characteristics • Due to differences between devices, each diode has a different voltage across it. • Would like to “Equalize” the voltages. Series-Connected Diodes with Voltage Sharing Resistors Series-Connected Diodes with Voltage Sharing Resistors Series-Connected Diodes with Voltage Sharing Resistors • Is = Is1+IR1 = Is2+IR2 • IR1 = VD1/R1 • IR2 = VD2/R2 = VD1/R2 • • • • Is1+VD1/R1 = IS2+VD1/R2 Let R = R1 = R2 Is1 + VD1/R = Is2 +VD2/R VD1 + VD2 = Vs Example 2.3 • Is1 = 30mA, Is2 = 35mA • VD = 5kV • (a) – R1=R2=R=100kΩ, find VD1 and VD2 • (b) – Find R1 and R2 for VD1=VD2=VD/2 Example 2.3 (a) Is1 = 30mA Is2 = 35mA R1 = R 2 = R = 100kΩ -VD = -VD1 - VD2 VD2 = VD - VD1 VD1 VD2 Is1 + = Is2 + R R VD R VD1 = + (IS2 -IS1 ) 2 2 5kV 100k VD1 = + (35Χ10-3 - 30Χ10-3 ) = 2750Volts 2 2 VD2 = VD - VD1 = 5kV - 2750 = 2250Volts Example 2.3 (a) simulation R1 100kOhm + U1 -2.727k V DC 1MOhm - D1 DIODE_VIRTUAL* V1 5000 V R2 100kOhm + - U2 -2.273k V DC 1MOhm D2 DIODE_VIRTUAL** Example 2.3 (b) Is1 = 30mA Is2 = 35mA VD = 2.5kV 2 VD1 VD2 Is1 + = Is2 + R1 R2 VD1 = VD2 = R2 = VD2R1 VD1 - R1(Is2 -Is1 ) R1 = 100kΩ 2.5kVΧ100kΩ R2 = 2.5kV -100kΩΧ(35Χ10-3 - 30Χ10-3 ) R2 = 125kΩ Example 2.3 (b) simulation R1 100kOhm + U1 -2.500k V DC 1MOhm - D1 DIODE_VIRTUAL* V1 5000 V R2 125kOhm + - U2 -2.500k V DC 1MOhm D2 DIODE_VIRTUAL**