Variable Gain Equalizer Circuit for PAM Waveform Distortion Control
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Solution Overview
Problem
Existing equalizer circuits for multi-level PAM signaling suffer from excessive amplification leading to waveform distortion and require large circuit area and power consumption due to separate amplifier and equalizer stages.
Innovation Solution
A variable gain equalizer circuit integrated on a semiconductor substrate, combining a high frequency emphasis filter and variable gain amplifier in a single stage with a variable resistor and capacitor, which suppresses excessive amplification and equalizes signals while maintaining uniform multi-levels, and can be further enhanced by coupling multiple stages in series with digitally controllable resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate amplifier and equalizer stages are used, then signal amplification and equalization can be achieved, but circuit area and power consumption increase
Solution Approach 1:
The patent combines the amplifier and equalizer into a single integrated circuit stage, where the same transistors and resistors perform both amplification and equalization functions simultaneously, eliminating the need for separate stages and reducing overall circuit area
Solution Approach 2:
The circuit components serve multiple functions: the differential amplifier provides both signal amplification and high-frequency emphasis through its feedback network, allowing a single circuit to perform what previously required separate dedicated amplifier and equalizer stages
2Reliability
If separate amplifier and equalizer stages are used, then signal amplification and equalization can be achieved, but power consumption increases
Solution Approach 1:
By merging the amplifier and equalizer into one circuit stage with shared components, the total power consumption is reduced compared to operating two separate stages, while still achieving both amplification and equalization of the signal
3Reliability
If conventional equalizer circuit is used, then equalization can be achieved, but excessive amplification causes waveform distortion
Solution Approach 1:
The patent introduces a variable gain control mechanism that adjusts the amplification factor dynamically, allowing the circuit to achieve proper signal equalization while preventing excessive amplification that would cause waveform distortion in multi-level PAM signals
Data Source
AI summary
An equalizer circuit includes a variable gain equalizer circuit. A third transistor MN for gain adjustment is coupled between a source of a first transistor that constitutes an input differential pair of the variable gain equalizer circuit, and a first current source IB. A fourth transistor MN for gain adjustment is coupled between a source of a second transistor that constitutes the input differential pair, and a second current source IB. A first bias voltage Vb is supplied to the gates of the third transistor MN and the fourth transistor MN, so as to enable DC gain control of the variable gain equalizer circuit.