Floating Transconductor Preamplifier for Fast Low-Power ADCs
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Solution Overview
Problem
High-speed preamplifier circuits for Analog-to-Digital converters require increased power and larger input capacitors, leading to accuracy issues and additional circuit area, while existing solutions fail to achieve high speed without consuming extra current.
Innovation Solution
A preamplifier circuit with capacitive positive feedback is implemented, using a transconductor circuit with active feedback only during amplification, which includes a floating transconductor stage that stores offset voltages and provides passive positive feedback to boost speed without increasing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high current is used in the preamplifier to achieve high-speed amplification, then the amplification speed is improved, but the power consumption increases and the input capacitor size increases leading to accuracy issues and additional circuit area
Solution Approach 1:
The circuit dynamically switches between two operational modes using clock signals: a first mode during the amplification phase where the first transconductor is active and provides high-speed amplification, and a second mode during the holding phase where the first transconductor is inactive and power consumption is reduced. This dynamic operation allows the circuit to achieve high amplification speed when needed while minimizing power consumption during the holding phase.
2Speed
If high current is used in the preamplifier to achieve high-speed amplification, then the amplification speed is improved, but the input capacitor size increases leading to accuracy issues and additional circuit area
Solution Approach 1:
The circuit dynamically switches between two operational modes using clock signals: a first mode during the amplification phase where the first transconductor is active and provides high-speed amplification, and a second mode during the holding phase where the first transconductor is inactive and power consumption is reduced. This dynamic operation allows the circuit to achieve high amplification speed when needed while minimizing power consumption during the holding phase.
3Speed
If increased power is consumed to achieve high-speed amplification, then the amplification speed is improved, but the accuracy deteriorates due to increased input capacitor size
Solution Approach 1:
The circuit employs feedback mechanisms where the second transconductor provides feedback to cancel offset voltages generated by the first transconductor during amplification. This feedback approach maintains amplification accuracy by actively compensating for errors introduced during high-speed operation, allowing the circuit to achieve both high speed and high accuracy simultaneously.
Solution Approach 2:
The circuit dynamically switches between two operational modes using clock signals: a first mode during the amplification phase where the first transconductor is active and provides high-speed amplification, and a second mode during the holding phase where the first transconductor is inactive and power consumption is reduced. This dynamic operation allows the circuit to achieve high amplification speed when needed while minimizing power consumption during the holding phase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high-speed amplification with reduced power consumption and smaller transistor sizes, minimizing circuit area and enhancing gain without additional current, thus improving accuracy and reducing offset and kickback noise.
Implementation Method 1
preamplifier circuit with capacitive, positive feedback
Implementation Method 2
The first transconductor receives a differential voltage from a sample-and-hold circuit and drives a floating transconductor. The first and floating transconductors output amplified versions of the differential voltage
Implementation Method 3
a transconductor circuit with active feedback only during amplification, which includes a floating transconductor stage that stores offset voltages
Data Source
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AI summary
A preamplifier circuit includes a first transconductor and a floating transconductor. The first transconductor receives a differential voltage from a sample-and-hold circuit and drives the floating transconductor. The first and floating transconductors output amplified versions of the differential voltage that are not affected by capacitive division, which makes the preamplifier circuit fast. The preamplifier circuit also has a low input capacitance because the floating transconductor is not connected to any external circuitry.