Logarithmic Amplifier Gain Blending for Wide Dynamic Range
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Solution Overview
Problem
Existing digital microphones face challenges in achieving low noise and distortion performance while handling wide signal swings without degrading signal-to-noise ratios (SNR), particularly in the context of market trends towards improved signal handling and reduced noise.
Innovation Solution
A logarithmic amplifier system is implemented using multiple amplifiers with different gains, where a transition shaping circuit controls the multiplication factors of these amplifiers to smoothly transition between gains, minimizing discontinuities and using a summing circuit to combine their outputs, thereby providing a continuous logarithmic transfer function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PGA amplifier is used to amplify the analog signal, then the circuit is simple, but the signal-to-noise ratio deteriorates when handling wide signal swings
Solution Approach 1:
The single amplifier is segmented into multiple amplifiers with different gains (first amplifier with gain G1, second amplifier with gain G2). Each amplifier handles specific signal swing ranges, allowing the system to maintain low noise performance across wide signal swings by selecting the appropriate amplifier segment for each input level.
Solution Approach 2:
The system dynamically switches between different amplifier gains based on the input signal level. The transition shaping circuit dynamically adjusts the multiplication factor K between 0 and 1, enabling the system to adaptively select the optimal amplifier for the current signal conditions, thus maintaining high signal-to-noise ratio across varying signal swings.
2Measurement precision
If multiple amplifiers with different gains are used to improve signal handling, then the signal-to-noise ratio improves, but discontinuities and delays are introduced
Solution Approach 1:
The transition shaping circuit ensures continuous and smooth transition between different amplifier gains by generating a multiplication factor K that changes continuously from 0 to 1 rather than switching abruptly. This continuous modulation of the gain transition eliminates discontinuities in the output signal and minimizes transition delays, maintaining uninterrupted signal processing.
3Adaptability or versatility
If logarithmic amplification is implemented to handle wide signal swings, then dynamic range improves, but noise performance may deteriorate
Solution Approach 1:
Different amplifiers are assigned different local gain characteristics (G1 for lower signal levels, G2 for higher signal levels). The transition shaping circuit locally modulates the gain contribution of each amplifier based on the current signal level, ensuring that each amplifier operates in its optimal noise performance region while collectively providing wide dynamic range coverage.
Data Source
AI summary
A logarithmic amplifier system is disclosed. The system includes first and second amplifiers respectively having first and second gains; a first multiplier having an input connected to an output of the first amplifier, and being configured to output a first multiplied signal based on an output signal of the first amplifier and based on a received first multiplication factor equal to a value K; a second multiplier having an input connected to an output of the second amplifier, and being configured to output a second multiplied signal based on an output signal of the second amplifier and based on a received second multiplication factor equal to 1 minus the value K; a transition shaping circuit configured to change the value K from 0 to 1 with a filtered transfer function; and a summing circuit having inputs coupled to outputs of the first multiplier and the second multiplier.