Low-Noise Amplifier Circuit With Gain Stability for Thermal Resistors

The patent combines the bias circuit and amplification circuit into a single integrated first stage amplifier. The bias circuit generates bias currents that are directly used by the amplification circuit, eliminating the need for separate large components and capacitors. This integration maintains low noise performance while significantly reducing the circuit area occupation.

The patent replaces traditional passive RC filtering components with active transistor-based filtering mechanisms. The first stage amplifier uses transistor circuits to achieve the same filtering and noise reduction functions that would traditionally require large capacitors and resistors, thereby reducing both area and complexity while maintaining noise performance.

The patent replaces large passive capacitors used for low-frequency biasing with active transistor-based biasing circuits. The bias circuit uses transistor current mirrors and active filtering to achieve the required low cut-off frequency without needing large physical capacitors, thereby maintaining biasing accuracy while reducing component size.

The patent uses parameter changes in transistor dimensions (scaling) to achieve gain stability. The gain recovery stage employs transistors with carefully selected size ratios that compensate for temperature-induced gain variations. By adjusting transistor width and length parameters, the circuit maintains stable gain across temperature ranges without requiring complex additional stabilization circuits.