Clocked Differential Amplifier for Wide Input Common Voltage
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Solution Overview
Problem
Existing analog/digital converters face challenges in stabilizing circuit operation over a wide range of input common voltages while maintaining low power consumption, as the source potentials of input transistors abruptly decrease to ground during amplification, limiting the applicability of sense amplifier configurations to preamps.
Innovation Solution
An amplifier design featuring a transistor pair with a constant current source and a switch controlled by a clock signal, allowing the amplifier to operate between two power supplies and maintain stable operation over a wide input common voltage range with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a sense amplifier configuration is used with input transistors having source potentials fixed to ground voltage, then power consumption is reduced by interrupting current during reset period, but the range of input common voltage must be narrowed to stabilize circuit operation
Solution Approach 1:
The patent embeds a constant current source within the amplifier circuit structure, nesting it between the second power supply and the transistor pair. This nested configuration allows the current source to continuously bias the input transistors while the clock-controlled switch manages power consumption externally, resolving the contradiction between low power consumption and wide input voltage range.
Solution Approach 2:
The patent applies preliminary action by maintaining the source potentials of the input transistors at a stable voltage level through the constant current source before the amplification period begins. This preliminary biasing ensures that the transistors are properly conditioned to handle a wide range of input common voltages, while the clock signal subsequently controls power consumption during operation.
2Measurement precision
If a preamp with constant current source is used between input transistor pair and power supply, then signal comparison accuracy is improved, but power consumption increases due to constant current flow
Solution Approach 1:
The patent applies periodic action by using a clock signal to control the switch transistor, which periodically connects or disconnects the constant current source from the second power supply. During the amplification period, the current flows to maintain signal comparison accuracy; during the reset period, the current is interrupted to reduce power consumption. This periodic control resolves the contradiction between measurement precision and power consumption.
Solution Approach 2:
The patent introduces dynamics by making the constant current source controllable through the clock signal, allowing it to dynamically switch between active and inactive states. This dynamic control enables the circuit to adapt its power consumption based on operational requirements while maintaining signal comparison accuracy when needed, resolving the static contradiction between precision and power usage.
3Device complexity
If input transistor source potentials abruptly decrease to ground voltage during amplification period, then circuit operation can be simplified, but the speed of output signal decrease strongly depends on input common voltage requiring narrowed voltage range
Solution Approach 1:
The patent introduces an intermediary element - the constant current source - between the second power supply and the transistor pair. This intermediary maintains stable source potentials for the input transistors, decoupling them from direct ground connection. The clock-controlled switch acts as another intermediary that manages power supply connection without directly affecting the transistor source potentials, thereby simplifying circuit operation while maintaining wide input voltage range adaptability.
Data Source
AI summary
An amplifier that is operated between first and second power supplies includes a transistor pair having control terminals to which input signals are input, a load resistor pair that is provided between each transistor of the transistor pair and the first power supply, a constant current source that is provided between the second power supply and the transistor pair, and a first switch that is connected with the constant current source in series between the second power supply and the transistor pair, the first switch being turned on or off in accordance with a clock signal.