SA5217

The SA5217 is a 75MHz postamplifier system designed to accept low level high-speed signals. These signals are converted into a TTL level at the output. The SA5217 can be DC coupled with the previous transimpedance stage using SA5210, SA5211 or SA5212A transimpedance amplifiers. The main difference between the SA5217 and the SA5214 is that the SA5217 does not make the output of A1 and input of A2 accessible; instead, it brings out the output of A2 and the input of A8 thus activating the on-chip Schmitt trigger function by connecting two external capacitors. The result is that a much longer string of 1s and 0s, in the bit stream, can be tolerated. This "system on a chip" features an auto-zeroed first stage with noise shaping, a symmetrical limiting second stage, and a matched rise/fall time TTL output buffer. The system is user-configurable to provide adjustable input threshold and hysteresis. The threshold capability allows the user to maximize signal-to-noise ratio, thereby insuring a low Bit Error Rate (BER).

An auto-zero loop can be used to replace two input coupling capacitors with a single Auto Zero (AZ) capacitor. A signal absent flag indicates when signals are below threshold. The low signal condition forces the TTL output to the last logic state. User interaction with this "jamming" system is available. The SA5217 is packaged in a standard 20-pin surface-mount package and typically consumes 40mA from a standard 5V supply. The SA5217 is designed as a companion to the SA5211/5212A and SA5210 transimpedance amplifiers. These differential preamplifiers may be directly coupled to the postamplifier inputs. The  A5210/5217, SA5211/5217 or SA5212A/5217 combinations convert nanoamps of photodetector current into standard digital TTL levels.