Differential Transmitter Circuit for Fast Phase Switching
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Solution Overview
Problem
Existing transmitters face challenges in supplying large currents for high-speed data transmission due to insufficient voltage at constant current sources, limited current supply for capacitive loads, and high common-mode noise requiring additional feedback circuits.
Innovation Solution
A transmitter design incorporating parallel-connected source follower amplifiers and common source amplifiers with a mirror configuration, eliminating the need for a common-mode feedback circuit, allows for high current supply during phase changes and reduces common-mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large current is supplied to positive node 1 and negative node 2 for high-speed operation, then phase change speed is improved, but voltage drop at resistive elements increases causing insufficient voltage at constant current sources
Solution Approach 1:
The transmitter is divided into two independent push-pull amplifying units, each with its own constant current sources (MS1, MS2 for first unit; MS3, MS4 for second unit). This segmentation allows each unit to operate independently with sufficient voltage headroom, enabling large current supply for rapid phase change without compromising the voltage required by individual constant current sources.
2Speed
If large current is supplied to capacitor Cload for rapid phase change, then charging speed is improved, but current supply capability is limited by constant current sources
Solution Approach 1:
The load capacitor Cload is divided into two separate capacitors (Cload1 connected to positive node 1, Cload2 connected to negative node 2), each driven by its own push-pull amplifying unit. This segmentation allows each constant current source pair to charge its respective capacitor independently, effectively doubling the total current supply capability and enabling rapid charging without being limited by a single constant current source.
3Object-affected harmful factors
If common-mode feedback circuit is added to reduce common-mode noise, then noise performance is improved, but device complexity increases
Solution Approach 1:
The common-mode feedback circuit is completely removed from the system. Instead of adding complexity to reduce common-mode noise, the invention extracts and eliminates this component by using two independent push-pull amplifying units with separate constant current sources, which inherently provide better noise performance without requiring additional feedback circuitry.
Data Source
AI summary
A transmitter for supplying a large current upon phase change of an output voltage is disclosed. The transmitter includes a first amplifying unit including a first amplifier including first NMOS and PMOS transistors connected by a common source thereof, and a second amplifier including a second PMOS and NMOS transistors connected by a common drain thereof while being connected with the first amplifier in parallel, a second amplifying unit including a third amplifier including third NMOS and PMOS transistors connected by a common source thereof, and a fourth amplifier including fourth PMOS and NMOS transistors connected by a common drain thereof while being connected with the third amplifier in parallel, and differential output nodes including a positive node connected to an output stage of the first amplifying unit, to which the common source of the first amplifier and the common drain of the second amplifier are connected, and a negative node connected to an output stage of the second amplifying unit, to which the common source of the third amplifier and the common drain of the fourth amplifier are connected.