Differential Transimpedance Amplifier With Direct Photodiode Input
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transimpedance amplifiers with directly connected photodiodes suffer from increased circuit complexity, noise, and higher supply voltage requirements due to additional amplifiers, which degrades high-frequency performance and increases costs.
Innovation Solution
A transimpedance amplifier design with a symmetrically connected photodiode directly to the input, eliminating additional components like capacitors and resistors, and incorporating a differential voltage compensation unit to adjust the operating point and minimize noise, while using a common supply voltage to reduce circuit complexity and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional amplifiers are added at the input of the transimpedance amplifier, then the photodiode can be connected directly without coupling capacitors, but the circuit complexity increases and noise performance deteriorates
Solution Approach 1:
The patent removes the unnecessary additional amplifier stage from the input of the transimpedance amplifier. By extracting this redundant component, the circuit achieves direct photodiode connection without coupling capacitors, maintaining high-frequency response while reducing circuit complexity and noise performance deterioration.
2Reliability
If additional amplifiers are added at the input of the transimpedance amplifier, then the photodiode can be connected directly without coupling capacitors, but the noise performance deteriorates
Solution Approach 1:
The patent removes the additional input amplifier that generates noise. By eliminating this noise-generating component while maintaining direct photodiode connection, the circuit achieves high-frequency response improvement without the harmful noise side effect.
3Reliability
If additional amplifiers are added at the input of the transimpedance amplifier, then the photodiode can be connected directly, but the supply voltage must be increased
Solution Approach 1:
The patent removes the additional amplifier stage that requires extra supply voltage. By extracting this component, the circuit maintains direct photodiode connection for high-frequency response while reducing the supply voltage requirement by at least two collector-emitter voltages.
4Device complexity
If coupling capacitors are used at the input, then the circuit is simpler, but the bandwidth and sensitivity are impaired
Solution Approach 1:
The patent removes coupling capacitors from the input circuit by eliminating the need for additional amplifiers. This extraction achieves direct photodiode connection, maintaining circuit simplicity while preserving and improving bandwidth and sensitivity performance.
5Device complexity
If coupling capacitors are used at the input, then the circuit is simpler, but the noise performance is impaired
Solution Approach 1:
The patent removes coupling capacitors and additional input amplifiers simultaneously. This extraction achieves a simpler circuit without the noise performance impairment that would result from keeping the additional amplifiers, as the direct connection eliminates both components.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a circuit containing a transimpedance amplifier for converting two input currents into two output voltages, having a first amplifier part containing a first input, to which a first input voltage is applied, and into which a first input current flows, and having a second amplifier part containing a second input, to which a second input voltage is applied and into which a second input current flows, wherein the first amplifier part and the second amplifier part are connected to a common supply voltage, the first amplifier part and the second amplifier part are connected to a common current source, the input of the first amplifier part and the input of the second amplifier part have a differing direct voltage, and the first amplifier part and the second amplifier part are designed such that an output voltage of the first amplifier part is proportional to the input current of the first amplifier part and an output voltage of the second amplifier part is proportional to an input current of the second amplifier part.