Zero Crossing Detector Circuit for Magnetic Transducer

This is a circuit that can be used to detects zero crossing in the output of a magnetic transducer within a fraction of 1 mV. Here’s the figure of the circuit;

 

The resistive divider, R1 and R2, biases the inputs 0.5 V above ground, within the common-mode range of the LM111. The output will drive DTL or TTL directly. Because the output must drive any capacitive loading for positive-going output signals, the value of R5 determines circuit speed (a lower value increases speed). An optional offset-balancing circuit using R3 and R4 is included in the schematic. [Circuit diagram source: National Semiconductor Application Notes]