Ladder DAC Circuit With Complementary Transistors for Voltage Precision
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Solution Overview
Problem
Existing digital to analog converters face challenges in precisely outputting a desired voltage level due to varying resistance values influenced by digital codes, making it difficult to maintain a constant output voltage.
Innovation Solution
A digital to analog converter design featuring a ladder circuit with pairs of transistors and resistors, where each transistor-resistor unit has a first transistor coupled in series and a second transistor in parallel, allowing for the generation of complementary control signals to determine an equivalent resistance, ensuring precise output voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transistor is used in each transistor-resistor unit, then the device complexity is reduced, but the output voltage precision deteriorates due to varying resistance values
Solution Approach 1:
Each transistor-resistor unit is segmented into two transistors (first and second transistors) that operate in complementary fashion. This segmentation allows the unit to provide a more stable equivalent resistance by distributing the resistance control across two devices, thereby improving output voltage precision while maintaining reasonable device complexity
Solution Approach 2:
The invention changes the resistance parameter by using complementary control signals to switch between first and second transistors. This parameter change strategy ensures that the equivalent resistance remains more constant across different digital code combinations, improving output voltage precision without significantly increasing overall device complexity
2Adaptability or versatility
If the resistance varies with digital codes, then the device adaptability is improved, but the output voltage stability deteriorates
Solution Approach 1:
The invention implements dynamic switching between first and second transistors based on digital code inputs. This dynamic operation allows the DAC to adapt to different digital codes while maintaining stable output voltage through complementary transistor action, where one transistor is turned on while the other is turned off, keeping the equivalent resistance relatively constant
3Measurement precision
If complementary control signals are applied to determine equivalent resistance, then the output voltage precision is improved, but the device complexity increases
Solution Approach 1:
The invention merges the control functions by applying complementary control signals to pairs of transistors within each unit. This merging approach allows precise equivalent resistance determination through coordinated transistor switching, improving output voltage precision while consolidating control logic rather than adding independent control circuits
Data Source
AI summary
A digital to analog converter (DAC) has a plurality of transistor-resistor units connected in a string. Each of the transistor-resistor units of the DAC has a pair of transistors that are turned on/off by a pair of complementary control signals. Since the two transistors of each transistor-resistor unit are positioned symmetrically, an equivalent resistance would be determined precisely according to received digital codes, such that an output voltage of the DAC could be adjusted precisely based on the equivalent resistance.