Variable-Gain Amplifier Using Current Mirrors for Low-Voltage Gain Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional variable-gain amplifiers in near-field communication devices face challenges with high signal processing time due to variable stray capacitances and limited voltage gain caused by decreasing supply voltage, leading to distortion and inefficiency.
Innovation Solution
A variable-gain amplifier design featuring two amplification branches with fixed resistive elements and current mirror arrays, driven by a digital control word, which allows for impedance matching and gain adjustment without capacitive attenuators, reducing silicon surface area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a drivable resistor array is used to adjust voltage gain, then the gain can be modified, but variable stray capacitances are introduced that slow signal processing time
Solution Approach 1:
The amplifier is divided into two separate branches (first amplification branch and second amplification branch) that operate in parallel. Each branch has its own fixed resistive element and current mirror array, allowing independent operation. This segmentation eliminates the need for a single drivable resistor array, thereby removing variable stray capacitances while maintaining gain adjustability through digital control of current mirrors.
Solution Approach 2:
The patent replaces the conventional drivable resistor array (electrical component with variable capacitance) with a digital control system that drives current mirror arrays. The gain adjustment is achieved through digital control words that switch current mirror configurations, substituting the mechanical/electrical variable resistor approach with a digital switching approach that has negligible capacitance effects.
2Use of energy by moving object
If the supply voltage is decreased to reduce power consumption, then energy efficiency improves, but the voltage gain reaches the ceiling limited by supply voltage
Solution Approach 1:
The patent introduces fixed resistive elements as intermediaries between the voltage input and current output stages. By converting the input voltage to a current signal through these fixed resistors, the amplifier can operate with low supply voltages while maintaining adequate gain. The current mirror arrays then provide additional gain multiplication without being directly limited by the low supply voltage, as they operate in the current domain rather than voltage domain.
Solution Approach 2:
The patent substitutes direct voltage amplification (which is limited by supply voltage) with a two-stage process: voltage-to-current conversion followed by current amplification. This substitution allows the amplifier to achieve high gain even with low supply voltage, as the current mirror stages can provide significant current gain that is then converted back to voltage without requiring high supply voltage headroom.
3Ease of operation
If a capacitive attenuator is used to adjust signal amplitude, then the amplitude can be controlled, but the silicon surface area increases and power consumption rises
Solution Approach 1:
The patent completely removes the capacitive attenuator from the receiver architecture. Instead of having separate amplification and attenuation stages, the invention uses a single variable-gain amplifier that can both amplify and attenuate signals by controlling its gain through digital control words. This extraction of the attenuator eliminates the associated silicon area and power consumption while maintaining full amplitude control capability.
Solution Approach 2:
The variable-gain amplifier is designed to be universal, performing both amplification and attenuation functions within a single device. By using fixed resistive elements and digitally controlled current mirror arrays, the amplifier can achieve gain values greater than 1 (amplification) or less than 1 (attenuation), replacing the need for separate capacitive attenuator and amplifier stages with a single multi-functional block.
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
This design achieves low distortion and stable signal processing with reduced power consumption, even at low supply voltages, while eliminating the need for capacitive attenuators and minimizing silicon usage.
Implementation Method 1
two voltage follower stages that are able to perform impedance matching on the differential signal so as to achieve virtual unity gain
Implementation Method 2
the use of the first resistive element advantageously allows a first conversion of the differential voltage signal into an AC differential current signal
Implementation Method 3
The configurable amplification stages are driven by the digital control word so as to make it possible to amplify the intermediate differential current signal depending on the value of the digital control word
Implementation Method 4
the use of the second resistive element advantageously allows a second conversion of the amplified intermediate differential current signal into an output differential voltage signal
Data Source
AI summary
A variable-gain amplifier includes two amplification and attenuation branches, and first and a second resistive elements that are coupled between the two branches. Each branch includes a voltage follower stage and a configurable amplification stage. The voltage follower stages are intended to receive a differential signal and are configured to deliver, via the first resistive element, an intermediate differential current signal. The amplification stages are intended to receive the intermediate differential current signal and a digital control word, and are configured to deliver, via the second resistive element, an output differential voltage signal depending on the value of the digital control word.