Amplifier Circuit With Resistor-Based Gain Adjustment for Noise Detection
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Solution Overview
Problem
Existing amplifiers face difficulties in gain adjustment due to dependence on mutual conductance (gm) of MOS transistors, leading to insufficient noise reduction in image signals affected by power supply voltage variations.
Innovation Solution
An amplifier configuration including a low-frequency amplifier circuit with specific transistor and resistance connections, and a high-frequency amplifier circuit with a constant current circuit and capacitor, allowing independent gain adjustment independent of MOS transistor gm, and incorporating a current mirror circuit for improved noise detection and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gain adjustment is performed using MOS transistor mutual conductance (gm), then the amplifier can amplify the input signal, but the gain adjustment becomes difficult and insufficient noise reduction occurs
Solution Approach 1:
The patent changes the parameter used for gain adjustment from MOS transistor mutual conductance (gm) to the resistance value of a dedicated adjustment resistor (Radj). By making the gain adjustable through a resistor value that can be easily changed, the system achieves both precise noise detection and easy gain adjustment without being constrained by transistor characteristics
Solution Approach 2:
The patent separates the gain adjustment function from the signal amplification function. The amplification is performed by the MOS transistor while the gain adjustment is independently controlled through a separate resistor (Radj) in the feedback path, allowing precise control of the noise detection signal gain without affecting the main signal path
2Measurement precision
If a simple amplifier circuit is used, then the device complexity is low, but the noise detection precision is insufficient
Solution Approach 1:
The patent introduces an intermediary resistor (Radj) in the feedback path that mediates between the amplification stage and the output. This resistor allows precise control of the feedback amount, enabling accurate noise detection while keeping the overall circuit structure relatively simple and modular
Data Source
AI summary
Provided is an amplifier that includes a first transistor including a gate terminal to which an applied input signal is input, where a current depending on the applied input signal flows through the first transistor. A gate terminal of a second transistor is connected to a load section, and a current depending on a change in a voltage of the drain terminal of the first transistor flows through the second transistor. A source terminal of the first transistor and a drain terminal of the second transistor are connected in common to a first resistance, and the current from the first transistor and the current from the second transistor flow through the first resistance. A third transistor supplies a current approximately equal to the current of the second transistor. The current supplied by the third transistor is output from an output end.