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| resources:eval:user-guides:ad-fmclidar1-ebz:hardware_afe [20 Sep 2019 11:28] – Cristian Orian | resources:eval:user-guides:ad-fmclidar1-ebz:hardware_afe [20 Sep 2019 11:29] – Cristian Orian | ||
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| <m>N = ((-122V-Vbias)*4096)/ | <m>N = ((-122V-Vbias)*4096)/ | ||
| - | where N is the DAC code and Vbias is the desired APD bias voltage in volts. If N = 0, Vbias is aorund | + | where N is the DAC code and Vbias is the desired APD bias voltage in volts. If N = 0, Vbias is around |
| At the single ended output, the resting voltage is approximately 1.0V. Loaded with 100Ω or higher load, the output can swing to 3V. This is equivalent to a 2VP-P swing. However, in case there is low frequency noise at the input current, the resting voltage is no longer a constant of approximately 1.0V. In order to mitigate this problem, a negative feedback circuit is used. The loop bandwidth must be low such that it doesn’t affect the useful narrow signal pulses received from the APD. | At the single ended output, the resting voltage is approximately 1.0V. Loaded with 100Ω or higher load, the output can swing to 3V. This is equivalent to a 2VP-P swing. However, in case there is low frequency noise at the input current, the resting voltage is no longer a constant of approximately 1.0V. In order to mitigate this problem, a negative feedback circuit is used. The loop bandwidth must be low such that it doesn’t affect the useful narrow signal pulses received from the APD. | ||
| Line 20: | Line 20: | ||
| The TIA output is fed to the ADA4950, a buffer which converts the signal from single-ended to differential. The differential gain is 1 and the output common mode voltage is set to about 1.4V via an input. The buffer inverting input //Vtilt//, which is programmable, | The TIA output is fed to the ADA4950, a buffer which converts the signal from single-ended to differential. The differential gain is 1 and the output common mode voltage is set to about 1.4V via an input. The buffer inverting input //Vtilt//, which is programmable, | ||
| - | <m>N = (Vtilt*4096)/ | + | <m>N = (Vtilt * 4096)/ |
| ---- | ---- | ||
resources/eval/user-guides/ad-fmclidar1-ebz/hardware_afe.txt · Last modified: 03 Jan 2021 22:04 by Robin Getz