Variable Gain Amplifier Envelope Tracking for RFIC Linearity
Solution Overview
Problem
Existing variable gain amplifier circuits for multimode RFICs face challenges in achieving high dynamic range, high accuracy, low noise, and high linearity while minimizing circuit area and consumption current, particularly in suppressing signal distortion for LTE signals with high PAPR.
Innovation Solution
A semiconductor device with a variable gain amplifier circuit that includes a detection circuit to adjust the DC voltage of transistors based on the input signal amplitude, allowing for envelope tracking and precise gain control across multiple amplifiers, reducing noise and increasing linearity without increasing circuit area or consumption current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If detection circuits are added to all 21 amplifiers to implement envelope tracking, then linearity and efficiency are improved, but circuit area and consumption current increase
Solution Approach 1:
The patent merges the detection function into a single shared detection circuit that serves all 21 amplifiers, rather than having separate detection circuits for each amplifier. This single detection circuit detects the input signal and generates detection currents that are distributed to control the bias circuits of all amplifiers, thereby implementing envelope tracking across the entire variable gain amplifier while minimizing circuit area and consumption current.
2Reliability
If power source voltage is increased to suppress signal distortion, then linearity is improved, but amplifier efficiency decreases
Solution Approach 1:
The patent implements dynamic power source voltage adjustment through envelope tracking. The power source voltage supplied to each amplifier is dynamically adjusted according to the amplitude of the input signal by controlling the bias circuits with detection currents. This allows the amplifier to operate with high power source voltage only when needed (during high signal amplitude periods), thereby maintaining high linearity while improving overall amplifier efficiency compared to using high power source voltage continuously.
3Measurement precision
If multiple amplifiers are coupled in parallel to achieve high dynamic range, then gain accuracy is improved, but noise and distortion increase
Solution Approach 1:
The patent applies envelope tracking feedback to each amplifier in the parallel configuration. A single detection circuit detects the input signal and generates detection currents that are fed back to control the bias circuits of all 21 amplifiers. This feedback mechanism dynamically adjusts the operating point of each amplifier according to the input signal amplitude, thereby suppressing distortion and noise while maintaining the high gain accuracy achieved through the parallel amplifier configuration.
Data Source
AI summary
A variable gain amplifier circuit includes output nodes, a plurality of amplifiers, and a detection circuit. The amplifiers are coupled in parallel with each other between the output nodes and a reference node and selectively assume an operating state in accordance with a control signal. The detection circuit outputs a detection signal according to the magnitude of an input signal to each amplifier. Each amplifier includes a first transistor, a second transistor, and a bias circuit. The first transistor receives, at its control electrode, the input signal or a signal proportional to the input signal. The second transistor is series-coupled to the first transistor between the first reference node and an output node. The bias circuit applies a DC voltage of a magnitude according to the detection signal to a control electrode of the second transistor.