Time gain compensation amplifier

Figure 9.6 shows the stability of the lifetime-based system here described over a period of 100 h of continuous operation. The sensor was immersed in saline solution in equilibrium with air at 760 torr. The intensity of the sensor decays with time due to the photodestruction of the porphyrin molecules (photobleaching). However, the lifetime value measured by the instrument remains relatively invariant over this period with a system drift of less than 1%. The instrument adjusts the gain of the programmable amplifier to compensate for the reduction in signal. 

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