69. Multi-Transistor Amplifiers : Amplifier With Active Load (Contd.) –Numerical Examples (Part B)
The chapter focuses on the common emitter (CE) amplifier with active loads and aims to highlight stability issues related to varying transistor parameters. It presents numerical examples comparing the performance of CE amplifiers with both active and passive loads, emphasizing the implications of changing early voltage and beta value on circuit stability and output characteristics. Solutions to enhance stability through negative feedback are also discussed.
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Sections
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What we have learnt
- Stability issues in amplifiers can arise from variations in transistor parameters such as early voltage and beta.
- Active load configurations can provide improved gain while making the output voltage sensitive to process variation.
- Proper configuration and selection of feedback resistors can mitigate instability and yield a reliable operating point.
Key Concepts
- -- Common Emitter Amplifier
- An amplifier configuration that uses a bipolar junction transistor to amplify signals, typically providing high gain.
- -- Active Load
- A load configuration that utilizes active devices (such as transistors) instead of passive resistors to increase gain and improve input/output characteristics.
- -- Stability Issues
- Problems that occur when circuit parameters, like beta or early voltage, vary, leading to shifts in operating points and performance degradation.
- -- Negative Feedback
- A technique where a portion of the output is fed back to the input to stabilize the operating point and improve overall performance.
- -- DC Operating Point
- The specific values of voltage and current in a circuit at which a device operates reliably and provides the desired signal amplification.
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