![]() The region between cut off and saturation is known as active r egion. If base current is greater than I B( sat), then collector current cannot increase because collector-base junction is no longer reverse-biased. At saturation, collector-base junction no longer remains reverse biased and normal transistor action is lost. At this point, the base current is maximum and so is the collector current. The point where the load line intersects the I B = I B( sat) curve is called sa turation. The collector-emitter voltage is nearly equal to V C C i.e. At cut off, the base-emitter junction no longer remains forward biased and normal transistor action is lost. At this point, I B = 0 and only small collector current ( i.e. The point where the load line intersects the I B = 0 curve is known as cut off. ( i) shows CE transistor circuit while Fig.( ii) shows the output characteristcs along with the d.c. For the common base configuration, when the input current I E was equal to zero, the collector current was equal only to the reverse saturation current I CO, so that the curve I E = 0 and the voltage axis were, for all practical purposes, one.The below Fig. Note on the collector characteristics of the figure that I C is not equal to zero when I B is zero. The cutoff region for the common emitter configuration is not as well defined as for the common base configuration. You will recall that these were the same conditions that existed in the active region of the common base configuration.The active region of the common emitter configuration can be employed for voltage, current, or power amplification. In the active region of a common emitter amplifier the collector-base junction is reverse-biased, while the base-emitter junction is forward-biased. shown this region exists to the right of the vertical dashed line at V CE(sat) and above the curve for I B equal to zero.The region to the left of V CE(sat) is called the saturation region. The active region for the common emitter configuration is that portion of the upper-right quadrant that has the greatest linearity, that is, that region in which the curves for I B are nearly straight and equally spaced. Consider also that the curves of I B are not as horizontal as those obtained for I E in the common-base configuration, indicating that the collector-to-emitter voltage will influence the magnitude of the collector current. Note that on the characteristics of common emitter configuration the magnitude of I B is in microamperes, compared to milliamperes of I C. That is,įor the common emitter configuration the output characteristics are a plot of the output current (I C) versus output voltage (V CE) for a range of values of input current (I B).The input characteristics are a plot of the input current (I B) versus the input voltage (V BE) for a range of values of output voltage (V CE).Ĭommon Emitter Configuration Characteristics: The emitter, collector, and base currents are shown in their actual conventional current direction.Even though the transistor configuration has changed, the current relations developed earlier for the common base configuration are still applicable. Two sets of characteristics are again necessary to describe fully the behaviour of the common emitter configuration one for the input or base-emitter circuit and one for the output or collector-emitter circuit. It is called the common emitter configuration since the emitter is common or reference to both the input and output terminals (in this case common to both the base and collector terminals). ![]() ![]() The most frequently encountered transistor configuration appears in Fig.
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