Transmitter Driver Current Compensation for Output Linearity
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Solution Overview
Problem
Integrated circuit transmitters face challenges in achieving high output linearity, which affects bit error rates in data communication systems, particularly due to variations in transistor sizes and operating voltages, and existing solutions do not adequately address these issues.
Innovation Solution
The proposed solution involves a transmitter driver circuit with a tail current path and pull-up current sources, along with a current compensation circuit that adjusts based on threshold voltages of transistors, to provide improved linearity and compensate for process, voltage, and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional transmitter circuits are used, then device complexity is low, but output linearity deteriorates due to transistor size and voltage variations
Solution Approach 1:
The patent changes the electrical parameters of the circuit by introducing variable current sources that adjust their output current based on transistor threshold voltage variations. The first current source adjusts its current proportionally to tail current variations, while the second current source compensates for threshold voltage effects, thereby maintaining output linearity across different process conditions without increasing structural complexity
Solution Approach 2:
The patent implements feedback mechanisms where the current sources are controlled by signals that reflect the actual operating conditions of the transistors. The control circuits monitor tail current and threshold voltage variations and adjust the current source outputs accordingly, creating a closed-loop system that actively compensates for process variations and maintains consistent output linearity
2Adaptability or versatility
If transistor sizes and operating voltages are varied, then adaptability improves, but output linearity deteriorates
Solution Approach 1:
The patent transforms the static current sources into dynamic components that automatically adjust their operating parameters in real-time. The current sources are designed to vary their output current based on the actual tail current level and transistor threshold voltages, enabling the circuit to adapt to different operating conditions while maintaining optimal output linearity through continuous parameter adjustment
Data Source
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AI summary
A circuit for generating a modulated signal in a transmitter of an integrated circuit is disclosed. The circuit comprises a transmitter driver circuit (302) having a first current path (325) for receiving a first input signal (Dataln) of a pair of differential input signals and a second current path (329) for receiving a second input signal (Dataln_b) of the pair of differential input signals, the transmitter driver circuit comprising a tail current path (327) coupled to each of the first current path and the second current path; a first current source (370) coupled between a first reference voltage (AVCCAUX) and ground (AVSS), wherein a first current of the first current source is proportional to the tail current of the tail current path; a first pull-up current source (460) coupled between the first reference voltage and a first output node (314) of the transmitter driver circuit; and a second pull-up current source (480) coupled between the first reference voltage and a second output node (320) of the transmitter driver circuit. A method of generating a modulated signal in a transmitter of an integrated circuit is also disclosed.