Lecture 4_ Jan 21 2011

Lecture 4_ Jan 21 2011 - Chapter 3 Solid-State Diodes and...

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Unformatted text preview: Chapter 3 Solid-State Diodes and Diode Circuits Chapter 13 Small-Signal Modeling and Linear Amplification Lecture 4 Cover sections: 3.6-3.8, 13.3, 13.4 Reverse Bias Saturation Current We earlier assumed that the reverse saturation current was constant. Since it results from thermal generation of electron-hole pairs in the depletion region, it is dependent on the volume of the space charge region. It can be shown that the reverse saturation gradually increases with increased reverse bias. I S = I S 1 + v R j I S is approximately constant at I S0 under forward bias. Chap 3.6 Reverse Breakdown Increased reverse bias eventually results in the diode entering the breakdown region , resulting in a sharp increase in the diode current. The voltage at which this occurs is the breakdown voltage , V Z . 2 V < V Z < 2000 V Chap 3.6 Reverse Breakdown Mechanisms Avalanche Breakdown Si diodes with V Z greater than about 5.6 volts breakdown according to an avalanche mechanism. As the electric field increases, accelerated carriers begin to collide with fixed atoms. As the reverse bias increases, the energy of the accelerated carriers increases, eventually leading to ionization of the impacted ions. The new carriers also accelerate and ionize other atoms. This process feeds on itself and leads to avalanche breakdown....
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Lecture 4_ Jan 21 2011 - Chapter 3 Solid-State Diodes and...

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