Bimodal Linear Equalizer With Complementary MOS Gain Peaking
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Solution Overview
Problem
Traditional linear equalizers (LEQs) are power hungry and ineffective at high data rates due to their amplifier loading characteristics, which degrade gain at low frequencies and boost it at high frequencies, limiting their ability to support high-speed signaling in memory systems.
Innovation Solution
The LEQ architecture employs complementary PMOS and NMOS devices to boost transconductance and output load resistance at high frequencies, enabling improved peaking without increasing power consumption or sacrificing low-frequency performance, and is designed as a bimodal LEQ to support both current and voltage mode signaling in a single receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional amplifiers with loading characteristics are used in LEQ, then gain peaking at Nyquist frequency is achieved, but power consumption increases and effectiveness at very high data rates is reduced
Solution Approach 1:
The patent changes the operating parameters of the transconductance devices by applying reverse bias to the substrate terminals. This parameter change modifies the device characteristics to reduce power consumption while maintaining the necessary gain peaking at the Nyquist frequency, directly resolving the contradiction between power efficiency and signal quality.
2Speed
If amplifier loading characteristics are used to boost gain at high frequencies, then high frequency performance is improved, but low frequency gain is degraded
Solution Approach 1:
The patent applies different characteristics to different frequency ranges by using transconductance devices with reverse biased substrates. This creates local quality optimization where the device provides appropriate gain characteristics for high frequencies through the reverse bias effect, while maintaining low frequency gain through the fundamental transconductance action, thus resolving the frequency-dependent gain contradiction.
3Device complexity
If traditional LEQ architecture is used, then circuit simplicity is maintained, but ability to support high-speed signaling (≥32 Gbps) is limited
Solution Approach 1:
The patent modifies the electrical parameters of existing transconductance devices by reverse biasing the substrate terminals. This parameter modification enhances the device performance to support higher data rates (≥32 Gbps) without changing the fundamental circuit architecture, thus achieving high-speed signaling capability while maintaining circuit simplicity.
Data Source
AI summary
A linear equalizer (LEQ) includes a first transconductance device coupled to an input node of the LEQ and a second transconductance device AC coupled to the input node of the LEQ to increase a gain of the LEQ for data signals above a predetermined frequency. The first transconductance device and the second transconductance device are of complimentary types. A bimodal LEQ includes inputs to control operation of the bimodal LEQ in a current mode or a voltage mode. The bimodal LEQ includes first and second transconductance devices. One of the first and second transconductance devices is AC coupled to an input node to increase the gain for data signals above a predetermined frequency.