Wideband Amplifier Circuit With Dual Frequency Peaking Control
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Solution Overview
Problem
Conventional amplifier circuits struggle to achieve desired frequency peaking characteristics over a wide band of 50 GHz or more, leading to signal loss compensation challenges in optical transmitters.
Innovation Solution
The proposed amplifier circuit combines a variable degeneration circuit and a variable negative capacitance circuit, with the degeneration circuit handling low-frequency peaking and the negative capacitance circuit handling high-frequency peaking, allowing for independent adjustment of peaking amounts to achieve desired frequency characteristics across a wide band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional frequency peaking method using inductors and variable resistors is used, then gain near a specific frequency is increased, but desired peaking characteristics cannot be realized over a wide band of 50 GHz or more
Solution Approach 1:
The amplifier circuit is divided into multiple stages: a first amplification stage with a first frequency peaking circuit and a second amplification stage with a second frequency peaking circuit. Each stage targets different frequency ranges, allowing the overall circuit to achieve wideband peaking characteristics covering 50 GHz or more while maintaining high gain across the entire bandwidth.
2Power
If variable resistors are adjusted to achieve peaking characteristics, then gain on high frequency side is increased, but DC gain fluctuates
Solution Approach 1:
Different circuits are assigned to handle different frequency ranges: the first frequency peaking circuit (with inductors and variable resistors) primarily affects high frequency gain, while the second frequency peaking circuit (with capacitors) primarily affects low frequency gain. This local specialization allows independent adjustment of high frequency peaking without significantly affecting DC gain stability.
Solution Approach 2:
The circuit employs feedback mechanisms where the output is fed back to control the peaking characteristics. The feedback loops allow the circuit to automatically adjust and stabilize DC gain while maintaining high frequency peaking, as the feedback detects DC gain variations and compensates for them.
3Power
If inductors are added to differential amplifier circuit, then frequency peaking characteristics are obtained, but device complexity increases
Solution Approach 1:
The frequency peaking circuits are designed to serve multiple functions: they provide frequency peaking characteristics, enable bandwidth extension to 50 GHz or more, and allow adjustable peaking amounts through variable components. The same circuit structures are used in both amplification stages, reducing design complexity through reuse and standardization.
Data Source
AI summary
An amplifier circuit comprises a variable degeneration circuit connected to emitter terminals of transistors, and a variable negative capacitance circuit connected to differential output signal terminals. The variable degeneration circuit includes a variable capacitor and a resistor. The variable negative capacitance circuit, which is a variable current source, includes a transistor, a capacitor, and a variable current source. The variable negative capacitance circuit includes transistors, a capacitor, and variable current sources.