Category Archive for: SMALL SIGNAL BJT AMPLIFIERS

THE DEPENDENCE OF SMALL-SIGNAL PARAMETERS ON DC BIAS CONDITIONS

Transconductance We h:I\’C seen that one of the important p.u amctcrs used in the truusistor models uf the last section the emitter resistance r., depends on the de bias current by way of the relation In fact. all small-signal parameters depend on dc operating conditions, some to a greater extent than others. Our goal now is to develop…

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The Effects of AC Load Resistance

Another way to view the voltage gain equation is to consider how gain varies as a function of ac load resistance ri- In order to focus on that aspect alone, let us assume that a CE amplifier is driven by a source having t:s ~ 0, so equation 5-42 becomes equations 5-17 and 5-18 that the ac…

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Small Signal CB Amplifier Model

An equivalent circuit for an electronic device is called a model. Using just the parameters we have discussed so far, we can construct a simple but reasonably accurate small-signal model for a transistor. Figure 5-23 shows a transistor in the common-base configuration and its approximate small-signal model. Remember that all voltages and currents are ac quantities, so all polarities…

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The Effect of Load Resistance on AC Operation

Let us now consider the effect of connecting a load resistor RI. across the output of the CE amplifier. Figure 5-17 shows the circuit we studied earl.er, modified to include a capacitor-coupled load resistor of 6 kfl. It is important to realize that as far as lie performance is concerned, R/. is ill parallel with Re. A de…

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Graphical Analysis of the Small Signal CE Amplifier

Our study of transistor amplifiers begins with an analysis of the common-emitter circuit, because that is the most widely used configuration. Figure 5-10 shows the CE bias circuit we studied in Chapter 4 modified by the inclusion of an ac signal source in s-erieswith the base. For the sake of completeness we include a coupling capacitor, but we will…

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load Resistance

An ac amplifier is always used to supply voltage, current, and/or power to some  kind of load connected to its output. The load may be a speaker, an antenna, a ‘siren, an indicating instrument, an electric motor, or anyone of a large number ofother useful devices. Often the load is the input to another ac amplifi er.…

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SMALL SIGNAL BJT AMPLIFIERS

In Chapter 4. we studied the de, l siettc, characteristics of transistors and used these to determine the dc output voltages and currents that resulted from the application of dc inputs. We wish now to investigate ~i tent to which small changes in the input voltage and current cause changes in the corresponding output quantities. We know, for example,…

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