SEMICONDUCTOR DIODES in Software

Drawer Code 3 of 9 in Software SEMICONDUCTOR DIODES

SEMICONDUCTOR DIODES
Code-39 Decoder In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
ANSI/AIM Code 39 Drawer In None
Using Barcode generation for Software Control to generate, create Code 39 image in Software applications.
Example 2.7. If both dc and time-varying sources are present in the original linear portion of a network, then vTh is a series combination of a dc and a time-varying source. Suppose that the Thevenin source for a particular network combines a 0.7-V battery and a 0.1-V-peak sinusoidal source, as in Fig. 2-10(a). Find iD and vD for the network. We lay out a scaled plot of vTh , with the vTh axis parallel to the vD axis of the diode characteristic curve. We then consider vTh , the ac component of vTh , to be momentarily at zero t 0 , and we plot a load line for this instant
Code 39 Extended Reader In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
Encode Code 39 Extended In Visual C#.NET
Using Barcode drawer for .NET framework Control to generate, create Code 39 Full ASCII image in .NET applications.
iD = id + IDQ
Drawing Code 39 Full ASCII In .NET
Using Barcode printer for ASP.NET Control to generate, create Code 39 image in ASP.NET applications.
Code 39 Creation In .NET Framework
Using Barcode encoder for VS .NET Control to generate, create Code39 image in .NET framework applications.
RTh = 10 W + VTh = 0.7 V _ +
Draw Code 3 Of 9 In Visual Basic .NET
Using Barcode encoder for .NET Control to generate, create Code 39 Extended image in .NET applications.
Encoding GTIN - 12 In None
Using Barcode printer for Software Control to generate, create UPC-A Supplement 5 image in Software applications.
LTh = 0.1 sin t (V)
Draw UCC.EAN - 128 In None
Using Barcode drawer for Software Control to generate, create GTIN - 128 image in Software applications.
Paint ANSI/AIM Code 39 In None
Using Barcode creation for Software Control to generate, create Code-39 image in Software applications.
+ + _
Creating Data Matrix 2d Barcode In None
Using Barcode creation for Software Control to generate, create ECC200 image in Software applications.
Barcode Creator In None
Using Barcode creation for Software Control to generate, create bar code image in Software applications.
LTh LD
USPS POSTal Numeric Encoding Technique Barcode Maker In None
Using Barcode creation for Software Control to generate, create Postnet 3 of 5 image in Software applications.
Drawing Data Matrix ECC200 In .NET Framework
Using Barcode creation for Reporting Service Control to generate, create Data Matrix ECC200 image in Reporting Service applications.
_ (a)
Code 128 Code Set B Decoder In None
Using Barcode decoder for Software Control to read, scan read, scan image in Software applications.
Scanning DataMatrix In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
iD, mA
EAN-13 Encoder In .NET
Using Barcode creator for Reporting Service Control to generate, create EAN-13 Supplement 5 image in Reporting Service applications.
Paint EAN / UCC - 14 In Objective-C
Using Barcode generation for iPhone Control to generate, create GS1-128 image in iPhone applications.
iD, mA
USS Code 39 Printer In VB.NET
Using Barcode generation for VS .NET Control to generate, create ANSI/AIM Code 39 image in Visual Studio .NET applications.
Bar Code Drawer In Visual C#.NET
Using Barcode drawer for VS .NET Control to generate, create bar code image in Visual Studio .NET applications.
80 70 60 50 44
Diode characteristic
a Idm
Q point DC load line
36 28
20 10 0
Dynamic load line
L D, V LTh, V
0.7 t (b)
Fig. 2-10
SEMICONDUCTOR DIODES
[CHAP. 2
on the diode characteristic. This particular load line is called the dc load line, and its intersection with the diode characteristic curve is called the quiescent point or Q point. The values of iD and vD at the Q point are labeled IDQ and VDQ , respectively, in Fig. 2-10(b). In general, a number of dynamic load lines are needed to complete the analysis of iD over a cycle of vTh . However, for the network under study, only dynamic load lines for the maximum and minimum values of vTh are required. The reason is that the diode characteristic is almost a straight line near the Q point [from a to b in Fig. 2-10(b)], so that negligible distortion of id , the ac component of iD , will occur. Thus, id will be of the same form as vTh (i.e., sinusoidal), and it can easily be sketched once the extremes of variation have been determined. The solution for iD is thus iD IDQ id IDQ Idm sin !t 36 8 sin !t where Idm is the amplitude of the sinusoidal term. mA
2.6. EQUIVALENT-CIRCUIT ANALYSIS Piecewise-Linear Techniques In piecewise-linear analysis, the diode characteristic curve is approximated with straight-line segments. Here we shall use only the three approximations shown in Fig. 2-11, in which combinations of ideal diodes, resistors, and batteries replace the actual diode. The simplest model, in Fig. 2-11(a), treats the actual diode as an in nite resistance for vD < VF , and as an ideal battery if vD tends to be greater than VF . VF is usually selected as 0.6 to 0.7 V for a Si diode and 0.2 to 0.3 V for a Ge diode. If greater accuracy in the range of forward conduction is dictated by the application, a resistor RF is introduced, as in Fig. 2-11(b). If the diode reverse current iD < 0 cannot be neglected, the additional re nement (RR plus an ideal diode) of Fig. 2-11(c) is introduced. Small-Signal Techniques Small-signal analysis can be applied to the diode circuit of Fig. 2-10 if the amplitude of the ac signal vTh is small enough so that the curvature of the diode characteristic over the range of operation (from b to a) may be neglected. Then the diode voltage and current may each be written as the sum of a dc signal and an undistorted ac signal. Furthermore, the ratio of the diode ac voltage vd to the diode ac current id will be constant and equal to vd 2Vdm vD ja vD jb vD dvD  rd 2:5 id 2Idm iD ja iD jb iD Q diD Q where rd is known as the dynamic resistance of the diode. It follows (from a linear circuit argument) that the ac signal components may be determined by analysis of the small-signal circuit of Fig. 2-12; if the frequency of the ac signal is large, a capacitor can be placed in parallel with rd to model the depletion or di usion capacitance as discussed in Section 2.3. The dc or quiescent signal components must generally be determined by graphical methods since, overall, the diode characteristic is nonlinear.
Example 2.8. For the circuit of Fig. 2-10, determine iD . The Q-point current IDQ has been determined as 36 mA (see Example 2.7). The dynamic resistance of the diode at the Q point can be evaluated graphically: rd vD 0:37 0:33 2:5  iD 0:044 0:028
Now the small-signal circuit of Fig. 2.12 can be analyzed to nd id : id vTh 0:1 sin !t 0:008 sin !t RTh rd 10 2:5 iD IDQ id 36 8 sin !t A
The total diode current is obtained by superposition and checks well with that found in Example 2.7: mA
CHAP. 2]
Copyright © OnBarcode.com . All rights reserved.