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1、Introduction,The ideal diode: (a) diode circuit symbol; (b) i-v characteristic; (c) equivalent circuit in the reverse direction; (d) equivalent circuit in the forward direction.,The Ideal Diode,Rectifier circuit,Rectifier Circuit,Output waveform.,Input waveform.,Equivalent circuit when v1 0,Equivale
2、nt circuit when v1 0,Rectifier Circuit Example 3.1,Rectifier Circuit Example 3.2,Terminal Characteristics of Junction Diodes Forward Region Example 3.3,Terminal Characteristics of Junction Diodes Reverse-Bias Region Exercise 3.9,Rectifier Circuit Exercises 3.4 and 3.5,The i-v characteristic of a sil
3、icon junction diode.,Diode i-v Characteristic,The diode i-v relationship with some scales expanded and others compressed in order to reveal details.,Diode i-v Characteristic,Thermal Voltage 25mV at room temp.,ln = 2.3 log,Diode i-v Characteristic Exercise 3.6 Consider a silicon diode with n=1.5. Fin
4、d the change in voltage if current changes from 0.1 mA to 10 mA.,Diode i-v Characteristic A diode for which the forward voltage drop is 0.7 V at 1 mA and for which n=1 is operated at 0.5 V. What is the value of the current?,Simplified physical structure of the junction diode. (Actual geometries are
5、given on Appendix A.),Diode Simplified Physical Structure,Diode Semiconductor Physics,The semiconductor diode is what is called a pn junction and is shown in the figure on the right Both the p and the n sections are part of the same crystal of silicon. At room temp., some of the covalent bonds in si
6、licon break and electrons are attracted to other atoms. These moving electrons leave a hole behind that is filled by another electron, thus continuing the cycle. In thermal equilibrium the concentration of holes (p) and the concentration of free electrons (n) are equal to each other and to ni which
7、is the number of holes or free electrons in silicon at a given temp. Study of semiconductor physics yields the following equation for the free electrons.,Diode Semiconductor Physics,Diode Semiconductor Physics,Diode Semiconductor Physics,Diode Semiconductor Physics,Diode Semiconductor Physics,Diode
8、Semiconductor Physics,Diode Physical Structure,Diode Physical Structure,Diode Physical Structure,Diode Physical Structure,Diode Physical Structure,Minority-carrier distribution in a forward-biased pn junction. It is assumed that the p region is more heavily doped than the n region; NA ND.,Diode Phys
9、ical Structure,Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Characteristic,Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Characteristic,Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Characteristic,Lessons In E
10、lectric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Characteristic,Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Applications,Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt,Diode Applications,Diode Applications,Diode Applications,Diode
11、 Applications,Diode Applications,A simple diode circuit.,Analysis of Diode Circuits,Graphical analysis of the circuit above,Graphical Analysis,Iterative Analysis Example 3.4,Approximating the diode forward characteristic with two straight lines.,Simplified Diode Models,Piecewise-linear model of the
12、diode forward characteristic and its equivalent circuit representation.,Simplified Diode Models Example 3.5,Development of the constant-voltage-drop model of the diode forward characteristics. A vertical straight line (b) is used to approximate the fast-rising exponential.,The Constant-Voltage Drop
13、Model,The constant-voltage-drop model of the diode forward characteristic and its equivalent circuit representation.,The Constant-Voltage Drop Model,Development of the diode small-signal model. Note that the numerical values shown are for a diode with n = 2.,The Small-Signal Model,Equivalent circuit
14、 model for the diode for small changes around bias point Q. The incremental resistance rd is the inverse of the slope of the tangent at Q, and VD0 is the intercept of the tangent on the vD axis.,The Small-Signal Model Example 3.6,The analysis of the circuit in (a), which contains both dc and signal
15、quantities, can be performed by replacing the diode with the model of previous figure, as shown in (b). This allows separating the dc analysis the circuit in (c) from the signal analysis the circuit in (d).,The Small-Signal Model,Circuit symbol for a zener diode.,Zener Diode - Characteristics,The di
16、ode i-v characteristic with the breakdown region shown in some detail.,Model for the zener diode.,6.8 V, 10mA 0.5W, 6.8-V, 70mA,Vz = Vzo + r2Iz Vz Vzo,Block diagram of a dc power supply.,Rectifier Circuits,(a) Half-wave rectifier. (b) Equivalent circuit of the half-wave rectifier with the diode repl
17、aced with its battery-plus-resistance model. (c) transfer characteristic of the rectifier circuit. (d) Input and output waveforms, assuming that rD R.,Rectifier Circuits,Full-wave rectifier utilizing a transformer with a center-tapped secondary winding. (a) Circuit. (b) Transfer characteristic assum
18、ing a constant-voltage-drop model for the diodes. (c) Input and output waveforms.,Rectifier Circuits,The bridge rectifier: (a) circuit and (b) input and output waveforms.,Rectifier Circuits,PIV,V,s,V,DO,-,Voltage and current waveforms in the peak rectifier circuit with CR T. The diode is assumed ide
19、al.,Rectifier Circuits With A Filter Capacitor,Rectifier Circuits With A Filter Capacitor,Rectifier Circuits With A Filter Capacitor,Rectifier Circuits With A Filter Capacitor,If Vp = 100 V R = 10 K Calculate the value of the capacitance C that will result in a peak-to-peak ripple Vr of 5 V, the con
20、duction angle and the average and peak values of the diode current.,The Spice Diode Model and Simulation Examples,The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonli
21、near depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. Reverse breakdown is modeled by an exponential increase in the
22、 reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers). name parameter units default example - - - - 1 IS saturation current A 1.0E-14 1.0E-14 * 2 RS ohmic resistance Ohm 0 10 * 3 N emission coefficient - 1 1.0 4 TT transit-time sec 0 0.1Ns 5 CJO z
23、ero-bias junction capacitance F 0 2PF * 6 VJ junction potential V 1 0.6 7 M grading coefficient - 0.5 0.5 8 EG activation energy eV 1.11 1.11 Si 0.69 Sbd 0.67 Ge,The Spice Diode Model and Simulation Examples,The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resi
24、stance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturatio
25、n current temperature exponent. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers). name parameter units default example a - - - - - 9 XTI saturation-current temp. exp - 3.0 3.0 jn 2
26、.0 Sbd 10 KF flicker noise coefficient - 0 11 AF flicker noise exponent - 1 12 FC coefficient for forward-bias - 0.5 depletion capacitance formula 13 BV reverse breakdown voltage V infinite 40.0 14 IBV current at breakdown voltage A 1.0E-3,PN Junction Diodes Name Parameter Units Default IS saturatio
27、n current A 1.0E-14 N emission coefficient - 1 BV reverse breakdown voltage V infinite RS diode series resistance 0 CJO zero-bias junction capacitance F 0 VJ junction potential V 1 M grading coefficient - 0.5,The Spice Diode Model and Simulation Examples,A variety of basic limiting circuits.,Limiting and Clamping Circuits,