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Full wave rectifier:
Full wave rectifier:
A full wave rectifier, known as an absolute value circuit, flips the negative input, making it all positive. Using operational amplifiers and diodes, the input is first half rectified, having the bottom half cut off as in the lower right image. At the same time, the input is put through a separate process which creates the other half of the wave, but inverted (upside down). Finally, these two halves are summed by an op amp to form the output, shown on the lower left image.
The final output in red; initial input in green
The final output in red; initial input in green
Half of the intermediate stage before being combined with its other half to form the output
Half of the intermediate stage before being combined with its other half to form the output
Comparator:
Comparator:
As explained in the general section, inductor coupling causes the wave to intermittently go down in voltage because of the load put on the reader's coil. After the waveform is rectified, the resulting wave is compared to a reference voltage to convert it to binary data.
Any input (Blue) above Vr (Red) will output a signal to ground (Green). Otherwise, the output will be high (5V)
Any input (Blue) above Vr (Red) will output a signal to ground (Green). Otherwise, the output will be high (5V)
The reference voltage is between the blue highs and lows, about where the yellow line is.
The reference voltage is between the blue highs and lows, about where the yellow line is.
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