Subject and UNIT: Electron Devices and Circuits: Unit V: (b) Oscillators
• The operation of the feedback amplifiers in which the negative feedback is used, has been discussed earlier. In this chapter, a device which works on the principle of positive feedback is discussed. The device is called an Oscillator.
Electron Devices and Circuits
Subject and UNIT: Electron Devices and Circuits: Unit V: (b) Oscillators
Electron Devices and Circuits: Unit V: (b) Oscillators : Syllabus, Contents
Feedback Amplifiers | Electron Devices and Circuits
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers : University Questions with Answers (Long Answered Questions)
Feedback Amplifiers | Electron Devices and Circuits
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers : Two Marks Questions with Answers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• Fig. 9.12.1 shows the transistor emitter follows circuit. Here, feedback voltage is the voltage across Ro and sampled signal is Vo across Re.
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• To analyse the feedback amplifier it is necessary to go through the following steps.
Solved Example Problems
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• Table 9.10.1 summarizes the effect of negative feedback on amplifier.
Feedback Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• If the feedback signal is added to the input in series with the applied voltage (regardless of whether the feedback is obtained by sampling the output current or voltage), it increases the input resistance.
Feedback Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• From equation Af = 1 / β we can say that if the feedback network does not contain reactive elements, the overall gain is not a function of frequency. Under such conditions frequency and phase distortion is substantially reduced by negative feedback.
Feedback Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• Now we analyse the effect of negative feedback on lower cut-off and upper cut-off frequency of the amplifier.
Feedback Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
Looking at equation (9.6.1) we can say that gain without feedback (A) is always greater than gain with feedback [AJ(1 + β A)] and it decreases with increase in P i.e. increase in feedback factor.
Feedback Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit V: (a) Feedback Amplifiers
• The basic amplifier shown in Fig. 9.3.4 may be a voltage, current, transconductance, or transresistance amplifier. These can be connected in a feedback configuration as shown in the Fig. 9.5.1.