Emitter Follower Amplifier Layout for Stable Feedback Gain
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Solution Overview
Problem
Conventional amplifying circuits experience gain fluctuations due to impedance changes in the negative feedback circuit, limiting their operation and introducing distortion in signal amplification.
Innovation Solution
The amplifying circuit employs a first stage with emitter follower circuits and transistors connected in a specific configuration to increase input impedance and stabilize gain, using transistors with collector currents determined by power source potentials and resistors to mitigate distortion, and includes a suppression circuit to stabilize operating points and reduce feedback circuit impedance contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a negative feedback circuit is connected between the inverting input terminal and output terminal, then the operational amplifier can function as an inverting or non-inverting amplifier circuit, but the gain fluctuates according to the impedance of the negative feedback circuit
Solution Approach 1:
The invention divides the amplification function into separate inverting and non-inverting amplifying circuits, each with dedicated input terminals. This segmentation allows independent optimization of each path while maintaining gain stability through separate feedback paths, resolving the contradiction between versatility and gain stability.
Solution Approach 2:
The invention employs asymmetric circuit configurations for inverting and non-inverting paths with different transistor arrangements and feedback mechanisms. This asymmetry enables each path to be optimized independently for its specific function while maintaining overall system stability, addressing the contradiction between adaptability and reliability.
2Reliability
If a constant current source is used to supply current to the differential amplifier circuit, then the collector currents are limited, but this limits the operation range and introduces distortion
Solution Approach 1:
The invention replaces static constant current sources with dynamic current supply mechanisms that can adapt to signal variations. This allows the collector currents to fluctuate according to input signal requirements while maintaining operational stability, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The invention dynamically changes current parameters based on signal conditions, allowing the operational amplifier to operate over a wider range without distortion. By adjusting current parameters adaptively rather than maintaining fixed constant current, the system achieves both stability and extended operation range.
3Reliability
If the emitters of transistors are connected to a constant current source, then the collector currents cannot fluctuate greatly, but this limits the amplification capability
Solution Approach 1:
The invention segments the current control into separate paths for inverting and non-inverting amplification, allowing independent current management in each path. This enables stable current control where needed while providing sufficient amplification power, resolving the contradiction between reliability and power capability.
Solution Approach 2:
The invention creates multi-functional transistor circuits that can operate in different modes (common emitter, common collector, differential) depending on the input signal. This universality allows the same circuit structure to provide both stable current control and high amplification capability, eliminating the need to choose between reliability and power.
Data Source
AI summary
The first emitter follower circuit and the second emitter follower circuit can increase an input impedance on the side of the inverting input terminal in the amplifying circuit. As a result, when a feedback circuit is connected between the inverting input terminal and the output terminal of the amplifying circuit, a fluctuation in a gain of the amplifying circuit according to a configuration of the feedback circuit can be suppressed.