Double Quench Circuit for Avalanche Photodiode Dead Time
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Solution Overview
Problem
Existing quench circuits for avalanche photodiodes face challenges such as prolonged 'dead time' due to RC time constants, increased heating from parasitic capacitance, and reduced sensitivity, especially when using active quench circuits on both anode and cathode sides.
Innovation Solution
A double quench circuit is implemented, featuring a passive quench circuit on the high voltage side and an active quench circuit on the low voltage side, along with detection and reset circuits to manage avalanche current effectively, reducing 'dead time' and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive quench circuit with a large current limiting resistor is used, then the avalanche current is effectively limited and the diode can be reset, but the RC time constant becomes large resulting in prolonged dead time
Solution Approach 1:
The quenching function is divided into two independent parts: a passive quench circuit connected to the cathode for current limitation, and an active quench circuit connected to the anode for rapid voltage restoration. This segmentation allows each circuit to operate optimally without being constrained by the RC time constant of a single large resistor.
Solution Approach 2:
A capacitor is introduced as an intermediary energy storage element between the high voltage source and the avalanche photodiode. This capacitor can rapidly discharge to restore the reverse bias voltage after an avalanche event, bypassing the slow charging process through the large current limiting resistor and thereby reducing dead time.
2Loss of time
If an active quench circuit is used to reduce dead time, then the reset speed is improved, but parasitic or intrinsic capacitance is introduced which increases charge flow and heating effect
Solution Approach 1:
Different quenching approaches are applied to different terminals of the avalanche photodiode: the cathode side uses a passive resistor-based approach with minimal added capacitance, while the anode side uses an active circuit for rapid response. This localized differentiation optimizes the balance between speed and heat generation.
3Speed
If traditional active quench circuits are used, then the avalanche current can be quickly stopped, but time delay is introduced in the circuit reducing sensitivity
Solution Approach 1:
The passive quench circuit is continuously active and ready to respond immediately to avalanche events, eliminating the need for activation delays inherent in traditional active quench circuits that require sensing and switching operations before quenching can begin.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The double quench circuit significantly reduces 'dead time', after pulsing, and heat dissipation, while enhancing the maximum count rate and linearity of the avalanche photodiode, allowing for faster reset and improved sensitivity.
Implementation Method 1
Photodiodes convert light into electricity and thus can be used to detect light levels
Implementation Method 2
an electron dislodged by a photon will hit other atoms in the APD semiconductor lattice with sufficient velocity and energy so that additional hole-electron pairs are created by the collisions
Data Source
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AI summary
A double quench circuit for an avalanche current device is provided in which the circuit includes an avalanche current device having a first terminal responsive to a bias voltage to reverse bias the avalanche current device above its avalanche breakdown voltage. A first quench circuit is responsive to the bias voltage and coupled to the first terminal of the avalanche device for reducing the amount of the avalanche current passing through the avalanche device. A second quench circuit is coupled to a second terminal of the avalanche device for reducing the amount of the avalanche current passing through the avalanche device.