Amplifier Bias Circuit With Mirror Current Source for Stable Linearity
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Solution Overview
Problem
Conventional bias circuits in amplifiers fail to maintain constant gain during variations in supply voltage, leading to reduced linearity and accuracy in output power, especially in 4G LTE/5G NR operations where amplifiers need to maintain power gain unchanged with increasing input power.
Innovation Solution
A bias circuit comprising a mirror current source and a current-to-voltage converter, where the mirror current source regulates the supply voltage using a reference voltage and preset parameter to generate a bias voltage that adjusts with supply voltage changes, ensuring accurate biasing across different voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bias circuit is used in the amplifier, then the circuit structure is simple, but the gain of the amplifier varies with input power, reducing linearity
Solution Approach 1:
The patent implements a feedback mechanism where the bias circuit monitors the input power level and adjusts the bias voltage accordingly. The bias circuit includes a feedback network that detects changes in input power and modifies the bias voltage to compensate for gain variations, thereby maintaining constant gain and improving linearity across different input power levels.
Solution Approach 2:
The bias circuit transitions from a static bias voltage approach to a dynamic adjustment mechanism. The circuit continuously adapts the bias voltage based on real-time input power conditions, enabling the amplifier to maintain optimal linearity characteristics across varying operating conditions rather than relying on a fixed bias point.
2Measurement precision
If the bias voltage is fixed, then the bias circuit is simple to implement, but the accuracy of bias voltage deteriorates when supply voltage varies
Solution Approach 1:
The bias circuit incorporates a feedback mechanism that continuously monitors supply voltage variations and adjusts the bias voltage accordingly. When supply voltage changes are detected, the feedback network modifies the bias voltage to compensate, ensuring that the bias voltage remains accurate and appropriate for the current operating conditions rather than remaining fixed.
Solution Approach 2:
The circuit dynamically changes the bias voltage parameter in response to supply voltage variations. Instead of using a fixed bias voltage, the circuit adjusts the bias voltage level based on the actual supply voltage conditions, ensuring optimal biasing accuracy across different supply voltage scenarios through parameter adaptation.
Data Source
AI summary
A bias circuit includes a mirror current source and a current-to-voltage converter. A first terminal of the mirror current source is connected to a supply voltage terminal, a second terminal of the mirror current source is connected to a reference voltage terminal, and a third terminal of the mirror current source is connected to the current-to-voltage converter. A mirror current source is configured to acquire a supply voltage transmitted at the supply voltage terminal through the first terminal, acquire a reference voltage transmitted at the reference voltage terminal through the second terminal, and regulate the supply voltage by using the reference voltage and a preset parameter to obtain a mirror current corresponding to the supply voltage. The preset parameter is parameter information of the mirror current source. The current-to-voltage converter is configured to convert the mirror current into a voltage to provide a bias voltage based on the voltage.