Posted on Mar 23, 2013 3707
Circuit has a 1 Hz-to-30 MHz output, 150-dB dynamic range, for a 0 to 5 V input. It maintains 0.08% linearity over its entire 71/3 decade range with a full-scale drift of about 20 ppm/Â°C. To get the additional bandwidth, the fast )FET buffer drives the Schottky TTL Schmitt trigger. The Schottky diode prevents the Schmitt trigger from ever seeing negative voltage at its input. The Schmitt`s input voltage hysteresis provides the limits which the oscillator runs between.
The 30-MHz, full-scale output is much faster than the LTC1043 can accept, so the digital divider stages are used to reduce the feedback frequency signal by a factor of 20. The remaining Schmitt sections furnish complementary outputs.