WiGig Baseband Amplifier With Current-Mirror Gain Decoupling
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Solution Overview
Problem
Conventional WiGig baseband signal-processing systems face challenges in achieving sufficient gain for maximum signal-to-noise ratio, attenuating out-of-band signals, and accommodating high dynamic range input signals while maintaining high linearity, particularly due to the interdependence of bandwidth and gain settings in filter-amplifier circuits, leading to high power consumption and sub-optimal design.
Innovation Solution
A circuit comprising a Sallen-Key filter and a programmable-gain amplifier, where the programmable-gain amplifier decouples bandwidth from gain settings through a current mirror copying ratio, and a source follower provides unity gain to independently control filter bandwidth and gain, reducing power consumption and improving linearity by ensuring adequate headroom for transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional filter-amplifier circuit is used with interdependent bandwidth and gain settings, then the circuit can provide filtering and amplification functions, but the power consumption increases and linearity deteriorates
Solution Approach 1:
The circuit is segmented into two independent functional blocks: a Sallen-Key filter for bandwidth control and a programmable-gain amplifier for gain control. This segmentation allows each block to be optimized independently, with the filter operating at unity gain to minimize power consumption and the PGA providing programmable gain with adequate headroom to maintain linearity.
Solution Approach 2:
A unity-gain buffer is introduced as an intermediary between the filter output and the PGA input. This buffer isolates the filter from the PGA's gain settings, preventing the PGA's impedance variations from affecting the filter's bandwidth characteristics, thereby enabling independent control of bandwidth and gain.
2Adaptability or versatility
If bandwidth and gain settings are interdependent in a filter-amplifier circuit, then the circuit can be simplified, but independent control of filter bandwidth and gain is lost
Solution Approach 1:
The circuit is divided into separate filter and amplifier sections with a unity-gain buffer in between. This segmentation provides independent control of bandwidth (via the Sallen-Key filter) and gain (via the programmable-gain amplifier), enhancing adaptability while maintaining manageable circuit complexity through modular design.
Solution Approach 2:
The unity-gain buffer serves multiple functions: it isolates the filter from the PGA, provides impedance matching, and enables independent control of bandwidth and gain. This multi-functionality allows the circuit to achieve high adaptability without proportionally increasing complexity.
3Measurement precision
If sufficient gain is provided for maximum signal-to-noise ratio, then the signal quality improves, but the dynamic range handling capability may be compromised
Solution Approach 1:
The programmable-gain amplifier provides dynamically adjustable gain through programmable impedance control, allowing the circuit to adapt to different input signal levels. This dynamic gain adjustment enables the system to maintain optimal signal-to-noise ratio for weak signals while handling high dynamic range inputs by reducing gain when necessary.
Solution Approach 2:
The PGA's gain parameter is made programmable through impedance control, allowing the gain to be changed based on input signal conditions. This parameter change capability enables the circuit to optimize signal-to-noise ratio for different signal levels while maintaining the ability to handle a wide dynamic range.
Data Source
AI summary
A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.