Differential Amplifier Topology for Low-Noise Low-Power Linearity
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Solution Overview
Problem
Conventional low noise amplifiers suffer from high noise levels, common mode stability issues, and require increased power levels, often necessitating four active input devices.
Innovation Solution
A low noise, low power differential two-stage amplifier architecture that uses a pair of input devices as a voltage source follower, with resistive elements and a feedback loop to provide voltage gain, and includes a gain transistor to enhance loop gain, while minimizing the number of input devices and passive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional instrumentation amplifier architecture with four active input devices is used, then noise performance is improved, but power consumption increases
Solution Approach 1:
The patent extracts and removes two of the four traditional active input devices from the amplifier architecture, retaining only one pair of input devices while using passive components (resistors and capacitors) to compensate for the removed active devices, thereby reducing power consumption while maintaining noise performance
Solution Approach 2:
The patent changes the configuration parameters by replacing active devices with passive components, specifically using a capacitor connected to ground and resistors to provide the necessary impedance matching and signal path functionality that would traditionally require active devices, thus reducing power consumption
2Reliability
If four active input devices are used in conventional amplifiers, then input impedance and signal buffering are improved, but device complexity increases
Solution Approach 1:
The patent removes two active input devices from the conventional four-device configuration, reducing device complexity while maintaining the essential input signal buffering function through the combination of one active device pair and passive component network
Solution Approach 2:
The patent introduces passive components (resistors and capacitors) as intermediary elements that mediate the signal path between the reduced number of active input devices and the rest of the amplifier circuit, compensating for the reduced active device count while maintaining proper signal buffering and impedance characteristics
3Power
If conventional differential difference amplifier architecture is used, then differential signal amplification is improved, but noise from tail current device increases
Solution Approach 1:
The patent removes the tail current device from the differential amplifier structure, eliminating the source of tail current noise while maintaining differential signal amplification capability through alternative circuit topology using passive components and a reduced set of active devices
Data Source
AI summary
A low noise, low power differential two-stage amplifier includes a first stage comprising a pair of electrical devices that sense an input signal difference across the pair of electrical devices; and a control feedback loop operatively connected to the first stage, wherein the first stage in combination with the control loop feedback is adapted to place an exact copy of the signal across a first pair of resistive components, wherein the first pair of resistive components are adapted to generate a differential signal current, wherein the control feedback loop is adapted to ensure that the differential signal current goes a second pair of resistive components to generate a voltage output. Preferably, the first and second pair of resistive components are in ratio to produce the exact copy of the signal with some gain at an output of the first stage.