Distributed Modulator Driver Input Biasing for PVT-Stable Linearity
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Solution Overview
Problem
Conventional amplifier circuits for optical transmitters are sensitive to process, voltage, and temperature variations, which affects their gain/bandwidth product and linearity, making it difficult to simultaneously optimize performance and yield.
Innovation Solution
Incorporating a current source in parallel with a resistor at the input of a distributed amplifier, which sets the bias voltage by reducing the current flowing through the resistor, thereby increasing the nominal bias voltage and reducing sensitivity to variations, while maintaining the gain and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bias voltage is increased to reduce sensitivity to PVT variations, then the gain/bandwidth product is improved, but the linearity deteriorates
Solution Approach 1:
The patent introduces a dynamically adjustable bias voltage system where the bias voltage can be adapted based on operating conditions. The bias voltage is set to a higher value during normal operation to reduce PVT sensitivity, while allowing adjustment to maintain linearity when required, thus resolving the contradiction between reliability and ease of operation
Solution Approach 2:
The patent changes the bias voltage parameter to a higher nominal value to reduce sensitivity to process, voltage, and temperature variations. This parameter change improves reliability while the system maintains the capability to adjust other parameters to preserve linearity when needed
2Productivity
If the bias voltage is increased to reduce sensitivity to PVT variations, then the yield is improved, but the performance optimization becomes more difficult
Solution Approach 1:
The patent implements a dynamic bias voltage adjustment mechanism that automatically adapts to different operating conditions. This reduces the need for complex manual optimization while improving yield through reduced PVT sensitivity, as the system self-adjusts to maintain optimal performance across process variations
Solution Approach 2:
The higher nominal bias voltage configuration enables the amplifier circuit to self-compensate for PVT variations without requiring complex external optimization circuits. The system inherently maintains better performance across process corners and temperature ranges, improving yield while reducing the complexity of performance optimization
3Reliability
If the current through the resistor is reduced to increase nominal bias voltage, then the sensitivity to PVT variations is reduced, but the gain and bandwidth may be affected
Solution Approach 1:
The patent employs a dynamic biasing scheme where the current through the resistor is adjusted to achieve the desired nominal bias voltage. The system dynamically balances the current reduction needed for higher bias voltage against the bandwidth requirements, maintaining both PVT stability and frequency response through adaptive control
Solution Approach 2:
The patent carefully selects and adjusts the resistor value and current source parameters to achieve the optimal balance. By changing these parameters, the system reduces the current through the resistor to increase nominal bias voltage and reduce PVT sensitivity, while compensating to maintain the required gain and bandwidth characteristics
Data Source
AI summary
The present disclosure relates to the field of amplifier circuits (driver amplifiers) for electro-optical modulators, in particular for amplifying an electrical signal for driving electro-optical modulators, an amplifier circuit is proposed for amplifying a signal comprising a gain amplifier, a distributed amplifier, a resistor, and a current source, wherein the input of the distributed amplifier is electrically connected to the output of the gain amplifier; the resistor terminates the input of the distributed amplifier; and the current source is electrically connected in parallel to the resistor. A method of setting a bias voltage of such an amplifier circuit is also proposed. Furthermore, a transmitter, in particular an optical transmitter, comprising such an amplifier circuit and a system comprising such a transmitter and a signal source are also proposed.