A Stable Amplifier

Chapter A Stable Amplifier

Complete Electronics Self Teaching Guide with Projects
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Complete Electronics Self Teaching Guide with Projects

  • CHAPTER 8 TRANSISTOR AMPLIFIERS330NOTE An amplifier whose gain and DC level bias point change as described in this problem is said to be unstable. For reliable operation, an amplifier should be as stable as possible. In later problems, you see how to design a stable amplifier.A STABLE AMPLIFIER11 You can overcome the instability of the transistor amplifier discussed in the first ten problems of this chapter by adding two resistors to the circuit. Figure 8.5 shows an amplifier circuit to which resistors RE and R2 have been added. R2, along with R1 (labeled RB in the pre-vious circuits), ensures the stability of the DC bias point.R1R2RCVC (DC bias level)REFIGURE 8.5By adding the emitter resistor RE, you ensure the stability of the AC gain.The labels in Figure 8.6 identify the DC currents and voltages present in the circuit. These parameters are used in the next several problems.R1R2RCVSVBIBICI1VCVEREI2VR = VS − VCVCE = VC − VEFIGURE 8.6Book Authorc08V107/04/2012 3:18 PM c08.indd 3307/4/2012 3:19:28 PM