Feedback in amplifiers
Feedback amplifiers are a type of electronic amplifier that use feedback to control and stabilize their performance. Feedback in amplifiers involves feeding a portion of the amplifier's output back to its input. This feedback mechanism can be used to modify the amplifier's gain, bandwidth, input and output impedance, and other characteristics. Feedback amplifiers are commonly used in a variety of applications due to their ability to provide precise control and improved performance. There are two main types of feedback amplifiers: positive feedback and negative feedback.
1. Negative Feedback Amplifiers:
- Negative feedback amplifiers are the most common type of feedback amplifiers.
- In these amplifiers, a portion of the output signal is fed back to the inverting input of the amplifier, which is often achieved using a resistive network or a voltage divider.
- Negative feedback reduces the overall gain of the amplifier and makes the circuit more stable, linear, and predictable.
- It also improves linearity, reduces distortion, widens the bandwidth, and lowers the output impedance, making the amplifier more suitable for a wide range of applications.
- Negative feedback amplifiers are widely used in audio amplifiers, operational amplifiers (op-amps), and other applications where precision and linearity are important.
2. Positive Feedback Amplifiers:
- Positive feedback amplifiers, in contrast, use feedback to increase the gain of the amplifier.
- They can introduce instability and are often used for specific applications where increased gain and oscillation are required.
- Common examples of positive feedback amplifiers include oscillators, where they are used to generate continuous waveforms or frequencies.
- Positive feedback amplifiers can be designed to produce specific frequency responses and waveforms, such as sine waves and square waves.
Benefits of Feedback Amplifiers:
- Improved Linearity: Negative feedback reduces distortion and improves linearity, making the amplifier more suitable for high-fidelity audio and precision applications.
- Stability: Negative feedback makes the amplifier more stable and less sensitive to variations in component parameters and operating conditions.
- Controlled Gain: Feedback allows precise control of the amplifier's gain.
- Wider Bandwidth: Negative feedback can extend the bandwidth of the amplifier.
- Lower Output Impedance: Negative feedback lowers the output impedance, making it easier to drive subsequent stages or loads.
In summary, feedback amplifiers are important in electronics for their ability to control and enhance the performance of amplifiers. Whether through negative or positive feedback, they play a crucial role in achieving specific design goals in various applications, including audio amplification, signal processing, and oscillation generation.