MOSFET Variable-Gain Amplifier Bias Control for Lower Current Draw
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Solution Overview
Problem
Existing variable-gain amplification circuits face challenges in reducing power consumption when multiple stages are connected, leading to increased current consumption and making them unsuitable for implementation as ICs, especially when dealing with wide input signal level variations.
Innovation Solution
A variable-gain amplification circuit design where the sources of MOSFETs are tied to a common connection point connected to a current source, with input signals supplied to the gates and drains connected to the sources of other MOSFETs, allowing for gain control through gate bias voltage adjustments to prevent operation in the three-pole tube region, thereby reducing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple variable-gain amplification circuits are connected in cascade to handle wide input signal level variations, then the adaptability to different signal levels is improved, but the current consumption increases proportionally with the number of stages
Solution Approach 1:
The patent combines multiple variable-gain amplification stages into a single integrated circuit architecture where stages share common current sources and biasing networks. This merging approach allows the circuit to handle wide signal level variations while the shared components reduce the total current consumption compared to separate cascaded circuits.
Solution Approach 2:
The amplification circuit is designed with multi-functional stages that can operate in different gain modes within the same circuit structure. The circuit can adapt to various signal levels by switching between operating modes rather than requiring separate dedicated circuits for each signal level range, thereby reducing overall current consumption.
2Adaptability or versatility
If MOSFETs are operated in the three-pole tube region to reduce gain, then the gain control range is improved, but the current consumption increases
Solution Approach 1:
The patent employs dynamic control of MOSFET operating regions through adjustable bias voltages. Rather than statically operating MOSFETs in the three-pole tube region for gain reduction, the circuit dynamically transitions MOSFETs between different operating regions (linear, saturation, and three-pole tube) based on the required gain level, optimizing current consumption at each gain setting.
Solution Approach 2:
The invention changes the operating parameters of MOSFETs by adjusting gate-source and drain-source voltages to control the operating region. By carefully managing these voltage parameters, the circuit achieves wide gain control range while avoiding the high current consumption associated with prolonged operation in the three-pole tube region.
3Ease of manufacture
If variable-gain amplification circuit is designed for IC implementation, then the integration is improved, but the power consumption control becomes more challenging
Solution Approach 1:
The patent segments the amplification function into multiple stages, each contributing to the overall gain control. This segmentation allows for better power management within the IC by enabling selective activation or deactivation of stages based on signal level requirements, thereby improving power consumption control while maintaining IC integration.
Solution Approach 2:
The invention incorporates feedback mechanisms that monitor the operating conditions and adjust bias voltages and gain settings accordingly. This feedback control enables the IC to optimize power consumption dynamically based on the actual signal levels and required gain, making power control more effective despite the challenges of IC implementation.
Data Source
AI summary
Disclosed herein is a variable-gain amplification circuit, wherein the sources of first and second MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are tied to a common connection point connected to a current source. An input signal is supplied to the gates of the first and second MOSFETs. The drains of the first and second MOSFETs are connected to the sources of third and fourth MOSFETs respectively whereas the drains of the third and fourth MOSFETs are connected to two output terminals respectively, a gain control voltage is supplied to the gates of both the third and fourth MOSFETs. When control is executed in order to lower the gain control voltage supplied to the gates of both the third and fourth MOSFETs, other control is also executed in order to raise a bias voltage applied to the gates of both the first and second MOSFETs.