Lecture12-DiodeSmalSignalModelZener

Lecture12-DiodeSmalSignalModelZener - ECE 3040:...

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ECE 3040 - Dr. Ying Zhang Georgia Tech ECE 3040: Microelectronic Circuits Lecture 12 Reading: Jaeger 3.4-3.14, 13.4, Pierret 9.2, Notes
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture pn Junction Capacitance () bi D A D A o S V junction Jo bi A Jo J V N N N N qK A C C V V C C A 1 2 1 0 + = = = = ε Junction capacitance is due to majority carrier charges displaced by the depletion width. Junction capacitance: t d Diffusion g C τ = T S D d V I I g + = Diffusion capacitance: Diffusion capacitance is due to “excess injected” minority carrier charge at the depletion region edges. Since this charge results from minority carriers, this capacitance is negligible at zero or reverse biases.
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture Large signal model of a diode (SPICE Model) ( ) 1) - (e I i V R i - v S D T Series D D η = R Series C Junction t d Diffusion g C τ = () A m bi A Jo J m bi o S o S V junction Jo V f V V C C and V qb K m AK C C A = + = = + + = 2 1 2 1 0 1 2 ε T S D d V I I g + =
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ECE 3040 - Dr. Ying Zhang Georgia Tech 1. Half wave rectifier 2. Peak detector 3. Peak detector with an RC load 4. LED 5. Photodiode Recapture Diode Applications
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ECE 3040 - Dr. Ying Zhang Georgia Tech Photodiode Reversed Bias Diode with no light illumination Reversed Bias Diode WITH light illumination results in “extra” drift current due to photogenerated ehp’s that can reach the junction. ¾ Photodiode = pn junction fabricated to permit light into the vicinity of the junction. ¾ Absorbed light creates EHPs in and near the depletion region.
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ECE 3040 - Dr. Ying Zhang Georgia Tech () ( ) L P N o V V o total Light to Due V V o total Light to Due dark total G L W L qA I e I I I e I I I I I T D T D + + + = + = + = 1 No-Light Light Light No-Light Bias Point I V Photodiode Every EHP created within the depletion region (W) and within a diffusion length away from the depletion region is collected (sweeped across the junction by the electric field) as photcurrent (current resulting from light). All other EHP’s recombine before they can be collected.
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ECE 3040 - Dr. Ying Zhang Georgia Tech Solar Cell = Unbiased Photodiode Light No-Light I V Since n p >n o and p n >p o at the junction edges, the voltage must be positive due to the law of the junction. = = = 2 ) ( ) ( ln i n n p p A n x x p x x n q kT V Current is “negative” or out of the p-type side (anode) Anode Cathode + - | I | V + - V Solar Cell acts as a battery producing power | I |
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ECE 3040 - Dr. Ying Zhang Georgia Tech ± Diode Small-Signal Model ± Breakdown Mechanisms Agenda
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ECE 3040 - Dr. Ying Zhang Georgia Tech Models used for analysis of Diode Circuits Mathematical Model (previously developed) Graphical Analysis Ideal diode Model •Treat the diode as an ideal switch
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This note was uploaded on 09/05/2009 for the course ECE 3040 taught by Professor Hamblen during the Spring '07 term at Georgia Institute of Technology.

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Lecture12-DiodeSmalSignalModelZener - ECE 3040:...

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