One of the simplest methods of improving SNR is to take multiple ADC samples of the base pulse level. The improvement is demonstrated in Figure 4-20. Increasing the number of base ADC samples from 1 to 20 improves the SNR at 1 nA from 13.8 to 19.1 when one signal ADC sample is taken. When five signal ADC samples are taken, the SNR at 1 nA improves from 15.6 to 31.3. A small amount of power consumption is required to keep the photo amplifier enabled and take the extra ADC samples, but this amount is insignificant compared to the LED power consumption.

tLED=100 µs

τ1=15 µs

τ2=15 µs

Figure 4-20 SNR at 1 nA With Varying Number of Base ADC Samples