Nested Transimpedance Amplifier Topology for Higher Gain-Bandwidth
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Solution Overview
Problem
Transimpedance amplifiers (TIAs) face limitations in achieving high gain-bandwidth product, particularly in applications requiring both high gain and bandwidth, such as optical sensors and high-speed hard disk drives, due to the inherent bandwidth constraints of existing TIA designs.
Innovation Solution
The solution involves 'nesting' a TIA within another TIA by adding additional circuit elements like feedback resistors, capacitors, and opamps on the input and output sides, which enhances the gain-bandwidth product by constructing first-order, second-order, or higher-order nested TIAs, allowing for increased bandwidth and gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional TIA designs are used, then the circuit structure is simple, but the gain-bandwidth product is limited
Solution Approach 1:
The patent applies nesting by placing a first TIA circuit inside a second TIA circuit, where the output of the inner TIA feeds into the outer TIA. This nested configuration allows the inner amplifier to provide initial gain while the outer amplifier extends the bandwidth, achieving a high gain-bandwidth product without requiring a single complex high-performance amplifier. The nested structure effectively combines multiple simpler stages to achieve superior overall performance.
2Speed
If bandwidth is increased using additional opamps, then the bandwidth requirement is met, but the circuit complexity increases
Solution Approach 1:
The patent segments the amplification function into multiple distinct TIA stages, each with specific gain and bandwidth characteristics. The first TIA circuit handles signal conditioning at the input stage, while the second TIA circuit provides additional amplification and bandwidth extension at the output stage. This segmentation allows each stage to be optimized independently, achieving high overall bandwidth while maintaining manageable complexity through modular design.
Data Source
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AI summary
A nested transimpedance amplifier (TIA) circuit includes a zero-order TIA having an input and an output, and a first operational amplifier (opamp). The opamp includes an input that communicates with said output of said zero-order TIA, a first transistor (2600) driven by said input, a second transistor (2602) that is driven by a first bias voltage (VB) and communicates with said first transistor (2600), a first current source (2604) that communicates with said second transistor (2602), and an output (Vout) at a node between the first transistor (2600) and the second transistor (2602).