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80. Differential Amplifier : Analysis and Numerical Examples (Contd.)(Part B)

80. Differential Amplifier : Analysis and Numerical Examples (Contd.)(Part B)

The chapter explores the integration of MOSFETs and BJTs in differential amplifiers, focusing on concepts such as biasing, current control, and gain calculations. It highlights the advantages of using active components over passive elements to improve performance, specifically in suppressing common mode signals while maximizing differential gain. Through extensive numerical examples, the chapter elaborates on the impact of various circuit parameters and the operational characteristics of the amplifiers.

Sections

Differential Amplifier with MOSFET and BJTs

This section discusses the functionality and design of a differential amplifier that integrates both MOSFETs and BJTs.

80.1 Section Overview

Start current section content and materials

80.1.1 Device Replacement

This section introduces the concept of replacing passive tail resistors with active devices in differential amplifiers, emphasizing their significance in improving common mode gain while maintaining differential signal integrity.

80.1.2 Current Characteristics

This section discusses the combination of BJTs and MOSFETs in a differential amplifier, focusing on current sources, biasing conditions, and the significance of input common mode range.

80.1.3 Biasing Conditions

The section explores the biasing conditions necessary for a differential amplifier using both BJTs and MOSFETs.

80.1.4 Input Common Mode Range

This section discusses the combination of MOSFETs and BJTs in a differential amplifier, specifically focusing on input common mode range and its implications on performance.

80.1.5 Common Mode Gain Calculation

This section discusses the calculation of common mode gain in a differential amplifier that combines MOSFETs and BJTs.

Summary of Today's Lecture

The lecture discusses the design and operation of a differential amplifier that integrates both MOSFETs and BJTs, focusing on their combined functionality and the impact on gain and common mode suppression.

80.2 Section Overview

Start current section content and materials

80.2.1 Focus on Numerical Examples

This section explores the interaction of MOSFETs and BJTs in differential amplifiers through numerical examples.

80.2.2 Conclusion

This section summarizes the key concepts regarding the differential amplifier and its significance in combining MOSFET and BJT technologies.

Learning Objectives

  • Differential amplifiers can effectively use both MOSFETs and BJTs when designed following fundamental principles.

  • The introduction of an active tail resistor significantly improves input common mode range and stabilizes operating points.

  • Common mode gain can be effectively reduced while maintaining high differential gain in amplifiers.

Key Concepts

Differential Amplifier

A circuit configuration that amplifies the difference between two input signals while rejecting any signals that are common to both inputs.

Common Mode Gain

The gain of the circuit when the same signal is applied to both inputs; a lower common mode gain indicates better performance for differential signals.

Active Tail Resistor

A circuit component that replaces passive resistors in the tail of a differential amplifier, enhancing performance by stabilizing currents and improving the common mode rejection ratio.

Biasing

The process of setting a DC operating voltage or current for a transistor to allow it to operate efficiently in the desired region of its characteristic curve.

Practice Exercises

Total Questions

3

Estimated Time

6 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting