I'm looking for a circuit that creates a precision amplitude square wave of 600kHz (50% duty cycle). The amplitude of the square wave needs to be 3Vpk-pk +/-10mV, but can be DC offset. The output of the circuit must be able to supply 100mA. The whole circuit is powered from a single sided 5-6VDC supply. The circuit is for a small sensor and would like to have consistency between them (i.e. 3Vpk-pk +/-10mV amplitude on each board).
My initial idea was
- generate a 3V precision power rail.
- Use a 555 timer circuit to generate the base square wave at 600kHz
- Feed the raw 600kHz square wave into a unity buffer rail-to-rail op amp circuit which has power rails of 0V and the precision 3V rail.
- The output should be a buffered square wave signal with 3Vpk-pk amplitude. My concern is that the rail-to-rail op amps still have some voltage drop between the supply rail voltage and the output voltage when it is at the rails and it could vary between boards/chips (I need consistency between multiple boards).
My second thought was to use a voltage limiting circuit (with 5V supply) and set the voltage limit levels to 1V (from precision reference) and 4V (from precision reference). Feed the 5Vpk-pk 600kHz square wave oscillator signal from the 555 timer into the voltage limiting circuit to get the 3Vpk-pk output at 600kHz.
Does anyone have any other thoughts or issue with these approaches, or perhaps better ideas for circuits to consider.