![]() If we can determine that the transistor is biased in active forward region, we can continue the design or analysis of dynamic situation using hybrid ∏ equivalent circuit.Īs we mentioned above, we can use different methods to calculate the quiescent point currents and voltages. Voltage divider biasing common emitter amplifier. Generally speaking, the transistor should be biased in the active forward region which means that we can use the constraint I C = βI B, and the voltage between collector and emitter V CE should be greater than V CES which stands for the critical saturation voltage and for small power transistors, we often think that V CES should be about 0.2 V - 0.3 V.įigure 1. As we all know, no matter which method is used, after we get the values of currents and voltages of quiescent point, we can determine the working region of the bipolar junction transistor. In this process, we do not ignore the base current and we can get accurate values of several voltages and currents. The second method is based on Thevenin equivalent methods. In the approach, we ignore the current of base called I B because in reality the base current is very small compared with the biased current through the two biasing resistors in almost all the cases. The first method is that we can use an approximate approach. ![]() In the first step, that is to say, during the quiescent point determination, we can deal with the circuit in two most common different ways. As we know, we can design or analyze the circuit from quiescent point to AC small-signal situation which means that we divide the problem into two steps. We can put this paper in the second region as we talked above.Īs shown in Figure 1, the voltage divider-based common-emitter amplifier is most popular in traditional textbooks and practical applications. Davidson described the nature of vacuum microelectronic integrated differential amplifier. Silva-Martinez did a research about graph approach for amplifiers. Zhang proposed a special common-emitter amplifier which can amplify voltage and current at same time. The second region is built on common and general problems. Yeo studied the reconstructing approaches. Rebeiz aim at how to improve the frequency characteristics and power gain. Yeo carried out their work focusing on new silicon-germanium alloy material devices and made great progress. The first region is the study of new material devices. We can classify the research into two different fields. Lots of scholars have carried out a lot of work from different directions. How to improve the characteristics of amplifiers is always one ongoing problem. The main function of the amplifiers is amplifying the weak signals so that the signal can become strong enough for practical applications. The main reason is that almost all the analog signals from the sensors are very weak and could not drive loads directly. An amplifier is one of the most important contents of electronic circuit systems.
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