Electro-Optical Modulator Driver Biasing for Lower PVT Sensitivity
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Solution Overview
Problem
Conventional amplifier circuits for optical communications are highly sensitive to process, voltage, and temperature variations, which affects their gain/bandwidth product and linearity, making it difficult to optimize performance and yield simultaneously.
Innovation Solution
Incorporating a current source in parallel with the resistor terminating the input of the distributed amplifier to set the bias voltage, reducing current flow through the resistor and increasing the nominal bias voltage of the gain amplifier, thereby reducing sensitivity to process, voltage, and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional amplifier circuit is used with a resistor terminating the input of the distributed amplifier, then the output impedance is matched, but the circuit is highly sensitive to process, voltage, and temperature variations
Solution Approach 1:
The patent changes the biasing parameter by replacing the conventional voltage divider bias with a current source bias. This parameter change makes the bias voltage independent of process, voltage, and temperature variations, thereby reducing PVT sensitivity while maintaining the gain/bandwidth product optimization
Solution Approach 2:
The patent introduces a current source as an intermediary element between the power supply and the amplifier circuit. This current source acts as a mediator that provides a stable bias current regardless of PVT variations, thereby decoupling the sensitivity from the gain/bandwidth performance
2Reliability
If the bias voltage is set using a voltage divider with a resistor, then the circuit is simple, but the bias voltage has limited margin to minimum bias voltage fluctuations
Solution Approach 1:
The patent changes the biasing parameter from voltage-based (voltage divider) to current-based (current source). This parameter change inherently provides a higher margin to minimum bias voltage fluctuations because the current source maintains a stable voltage drop across the terminating resistor, thereby improving reliability without significantly increasing complexity
Data Source
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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 (101) is proposed for amplifying a signal comprising a gain amplifier (102), a distributed amplifier (103), a resistor (Rg), and a current source (104), 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.