Need to repair a legacy system that has been discontinued and am considering replacing the PNP based circuit with the diode based circuit.
The input signal (max. freq = 20Khz) is applied at IN and is active low. It's TTL level.
The output is tapped from OUT and 3.3V is applied to this point through a weak pullup.
- Given this information, are both the circuits equivalent as far as IN and OUT digital signals are concerned?
- Is the PNP based circuit effectively a 3.3V level convertor?
- Is the diode based circuit an equally effective 3.3V level convertor?
- Why would a company prefer the PNP based circuit over the diode based circuit?