Greetings,
I am working on a Lidar system for a senior project and am running into issues I am unable to solve with my circuit. The project requires the use of an amplification and comparator circuit in order to take the detector output up to a level that will trigger a TDC controlled by a MSP430. The detector output voltages are around 2 mV and in order to trigger the TDC we require a >3.3 V signal, thus the ampflifier and comparator. The system requires high speed components in order to maintain the integrity of the time of flight calculations so I chose the OPA657 decomponsated op-amp for its greater performance, and planned on adding external compensation to account for this.
I used Texas Instruments simulating software to simulate the design(included in the link below) and saw that I got the amplification and timing I wanted. I saw no signs of oscillation at this point. When moving to actually building the circuit however measuring the output of the amplifier with an oscilloscope revealed low frequency oscillations. I have tried active bandpass filters, low & high pass filters, DC block at the input, and used suggested resistor/capacitor values to reduce oscillations as seen in the datasheets. The circuit is currently mounted on a demo-board designed for this kind of op-amp, so I am at a loss as to the source of these oscillations. Even with a basic non-inverting setup, there were still oscillations.
If anyone has any insight into this problem or anything I can try, help would be very much appreciated. I am including links at the bottom to the basic non-inverting setup, and can try to answer any questions to the best of my ability or post anything you need to see. Thanks.
Circuit Setup(non-inverting):
I am working on a Lidar system for a senior project and am running into issues I am unable to solve with my circuit. The project requires the use of an amplification and comparator circuit in order to take the detector output up to a level that will trigger a TDC controlled by a MSP430. The detector output voltages are around 2 mV and in order to trigger the TDC we require a >3.3 V signal, thus the ampflifier and comparator. The system requires high speed components in order to maintain the integrity of the time of flight calculations so I chose the OPA657 decomponsated op-amp for its greater performance, and planned on adding external compensation to account for this.
I used Texas Instruments simulating software to simulate the design(included in the link below) and saw that I got the amplification and timing I wanted. I saw no signs of oscillation at this point. When moving to actually building the circuit however measuring the output of the amplifier with an oscilloscope revealed low frequency oscillations. I have tried active bandpass filters, low & high pass filters, DC block at the input, and used suggested resistor/capacitor values to reduce oscillations as seen in the datasheets. The circuit is currently mounted on a demo-board designed for this kind of op-amp, so I am at a loss as to the source of these oscillations. Even with a basic non-inverting setup, there were still oscillations.
If anyone has any insight into this problem or anything I can try, help would be very much appreciated. I am including links at the bottom to the basic non-inverting setup, and can try to answer any questions to the best of my ability or post anything you need to see. Thanks.
Circuit Setup(non-inverting):
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