Amplifier Circuit With Voltage-Dependent Current for Higher Linearity
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Solution Overview
Problem
Conventional amplifier circuits improve linearity by subtracting drain current using cross-coupled transistors, but this results in lowered gain and increased power consumption due to bias current.
Innovation Solution
An amplifier circuit configuration that includes a transistor, a load connected to a power supply, an impedance element connected to the transistor's ground terminal, and a variable current source that supplies current based on the voltage of the connection part, supplementing the transistor's characteristics without lowering gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cross-coupled transistors are used to subtract and combine drain current to improve linearity, then linearity is improved, but gain is lowered
Solution Approach 1:
The patent changes the functional parameter of the impedance element from a fixed value to a variable value that changes with voltage. The impedance element has a first impedance value at a first voltage and a second impedance value at a second voltage, allowing the circuit to maintain high gain at low voltages while achieving improved linearity at higher voltages where the impedance changes. This parameter transformation resolves the contradiction by making the impedance adaptive rather than fixed.
2Manufacturing precision
If cross-coupled transistors are used to subtract drain current to improve linearity, then linearity is improved, but power consumption increases due to bias current
Solution Approach 1:
The patent implements periodic or conditional action through the voltage-dependent impedance element. The impedance element only exhibits its linearity-improving impedance characteristics when a specific voltage threshold is reached. During normal operation at lower voltages, the impedance element maintains low impedance to minimize power consumption. This conditional activation resolves the contradiction by making linearity enhancement power-efficient and only active when needed.
3Device complexity
If an impedance element with fixed impedance is used, then circuit simplicity is maintained, but linearity cannot be improved without lowering gain
Solution Approach 1:
The patent transforms the impedance element from a fixed-parameter component to a variable-parameter component whose impedance changes with applied voltage. This allows a single element to perform multiple functions: maintaining low impedance for simplicity and gain at operating voltages, and exhibiting high impedance for linearity improvement at saturation voltages. The parameter change approach maintains circuit simplicity while achieving linearity enhancement.
Data Source
AI summary
Linearity is improved in an amplifier circuit without lowering gain.The amplifier circuit includes a transistor, a load, an impedance element, and a variable current source. The transistor amplifies an input signal. The load is connected between the transistor and a power supply. The impedance element is connected between the transistor and a ground terminal, and passes a direct current. The variable current source is connected to a connection part between the transistor and the impedance element, and supplies a current in accordance with a voltage of the connection part.