Semiconductor Signal Amplifier Ladder Network Gain Control
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Solution Overview
Problem
Existing semiconductor devices for signal amplification in UMTS transmission systems face challenges in achieving high dynamic range, fine resolution, and low power consumption while minimizing noise and occupied area, particularly in mobile terminals where the number of amplifier stages increases noise and power consumption.
Innovation Solution
A semiconductor device with a ladder network and logic control circuit that selectively enables transconductance stages according to a control word, allowing for fine gain resolution and reduced power consumption by weighting input signals and converting voltage to current, thereby reducing the number of stages and consumption current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of amplifier stages is increased to achieve high dynamic range, then the gain control range is improved, but the total noise increases due to noise amplification at each stage
Solution Approach 1:
The amplifier is divided into multiple stages with different functions: a variable gain amplifier stage for fine gain adjustment and a fixed gain amplifier stage for bulk amplification. This segmentation allows the variable gain stage to operate at lower gain levels, reducing noise accumulation while still achieving high dynamic range through coordinated operation of both stages.
2Object-affected harmful factors
If the gain of high-frequency unit is controlled to suppress LO leakage at low power output, then the LO leakage is reduced, but the power consumption increases
Solution Approach 1:
The amplifier employs dynamic gain distribution where the variable gain amplifier and fixed gain amplifier stages are selectively activated based on the required output power level. At low power levels, only the variable gain stage operates with minimal gain, suppressing LO leakage. At high power levels, both stages are activated to distribute the gain requirement, reducing the burden on the variable gain stage and thereby suppressing LO leakage while maintaining efficiency.
3Measurement precision
If a very fine step of gain resolution (0.25 dB) is required inside RF-IC, then the variable gain resolution is improved, but the device complexity increases
Solution Approach 1:
The gain control function is segmented between a variable gain amplifier providing fine resolution control (0.25 dB steps) and a fixed gain amplifier providing coarse gain levels. This segmentation allows the variable gain stage to focus on fine adjustment with fewer control bits, reducing complexity while achieving the required 0.25 dB resolution through the combination of both stages.
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 dynamic range and fine resolution with reduced noise and power consumption, mitigating the issues of increased noise and power consumption associated with multiple amplifier stages, while maintaining a compact form factor suitable for mobile terminals.
Implementation Method 1
plural transconductance stages arranged corresponding to each node of the ladder network, and a logic control circuit which sets the first transconductance stages to an enabled state selectively according to a control word
Implementation Method 2
A semiconductor device with a ladder network and logic control circuit that selectively enables transconductance stages based on a control word, allowing for fine gain resolution and reduced consumption current by weighting input signals
Data Source
AI summary
A semiconductor device for transmitting-signal amplification which has a fine resolution, a high dynamic range, a small occupied area, and low power consumption, is realized. An input signal amplitude is reduced every one half by a ladder network, and a transconductance amplifier stage is arranged corresponding to each node of the ladder network. An output of the transconductance amplifier stage is coupled to an output signal line in common. According to a control word WC<21:0>, the transconductance amplifier stage is enabled selectively, and the output current which appears in the output signal line is added.