First show the overall design ideas, and then explain the purpose and principles of the design in steps. The common-emitter amplifier circuit is a typical inverting amplifier, which has a wide range of applications and stable effects. The overall design idea is: quantitatively determine the voltage and current to calculate the resistance. Therefore, the selected values of some experimental values can be used for reference. Usually, careless design will cause clipping and distortion of the output waveform. The cumbersome part of the transistor circuit lies in the setting of the static operating point. The parameters of the transistor circuit can all be obtained according to VBE=0.6V and Ohm's law. Among them, the base-emitter tube voltage drop VBE is also a very important parameter, which is generally equal to 0.6V (silicon tube). In addition, the calculation of gain is the external circuit resistance not the rbe. Therefore, in the general design process, the existence of the base current is ignored in an approximate calculation (In some circuits, although the base current is ignored, it is still necessary to give the base a certain current drive to make the circuit working normally). At the same time, it is very cumbersome to consider the base current in the specific calculation. When designing a circuit in non-extreme situations, we often hope that the circuit can work with most general-purpose transistors, avoiding the parameter that depends on component parameters such as rbe. But generally the emitter will have a resistance to control the gain, so the above formula is not practical. Rc/rbe Thus, we can get an inverted amplified voltage signal by AC coupling and controlling the collector resistance Re.Rc/rbe △Vi/rbe=△ib Thus, the collector generates a current of β times ib: △ie=β△ib Furthermore, the output voltage can be obtained by the relative positive power supply potential: △Vo=VCC-△ieRc=VCC-β△ibRc=VCC-△Vi.Transistor Common-emitter Amplifier Circuit Here, take the common emitter amplifier circuit as an example:įigure 1. Ⅲ Common-emitter Amplifier Circuit Expansion Ⅱ Common-emitter Amplifier Circuit Design Ⅰ Common-emitter Amplifier Circuit Formula Transistor Amplifiers Circuit Introduction Catalog This article will introduce how transistor works in the common-emitter amplifier circuit. Through the amplification of the transistor, the base current is generated between the collector and the emitter by β times. So the base current is very small, and may only be a few tenths of mA. In the small-signal model, the source of the base current is the ratio of the input voltage to the base-emitter dynamic resistance rbe, which is usually kΩ. In a general voltage amplification occasion, this amplification effect comes from the use of resistors to convert current into voltage. For example, control the collector-emitter current by changing the base current. The transistor is a current-control device.
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