Linear Equalizer Circuit Using Self-Biased RC Networks
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Solution Overview
Problem
Conventional linear equalizers enforce more gain reduction on lower frequency components of input signals rather than providing more gain enhancement for higher frequency components, requiring additional amplification to compensate for the gain reduction.
Innovation Solution
A linear equalizer circuit design that uses a combination of PMOS and NMOS transistors in self-biased RC networks to provide higher impedance for higher frequency signals, allowing for greater gain enhancement of high frequency components without sacrificing low frequency signal gain, eliminating the need for subsequent wide-band amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RC-degeneration network is used to provide frequency-dependent gain reduction, then equalization function is achieved, but gain of low frequency components is reduced requiring additional wide-band amplifier
Solution Approach 1:
The patent inverts the conventional approach by using self-biased MOS transistors with RC networks to provide frequency-dependent gain enhancement instead of gain reduction. The self-biasing mechanism creates an impedance that increases with frequency, thereby boosting high-frequency components while preserving low-frequency gain, eliminating the need for additional wide-band amplifiers.
Solution Approach 2:
The patent changes the operating parameters of MOS transistors by introducing self-biasing RC networks that dynamically adjust the transistor bias point based on frequency. This parameter change enables the transistor to provide higher impedance and gain enhancement at high frequencies while maintaining appropriate gain at low frequencies, resolving the contradiction between equalization and overall signal gain.
2Adaptability or versatility
If higher degree of equalization is required, then more gain reduction on low frequency component is needed, but this increases device complexity
Solution Approach 1:
The patent employs self-biased MOS transistors that automatically adjust their operating point and impedance characteristics based on the input signal frequency. The self-biasing RC networks provide frequency-dependent feedback that enables the transistor to enhance high-frequency gain without requiring external control circuits or additional amplification stages, achieving high-degree equalization while maintaining circuit simplicity.
Data Source
AI summary
A circuit having a first MOS transistor of a first type configured in a common-source amplifier topology for receiving an input signal and outputting an intermediate signal, a first MOS transistor of a second type configured in a self-biased topology biased via a first self-biasing RC network for providing termination for the intermediate signal, a second MOS transistor of the second type configured in a common-source amplifier topology for receiving the intermediate signal and outputting an output signal, and a second of MOS transistor of the first type configured in a self-biased topology via a second self-biasing RC network for providing termination to the output signal.