Hi,
How can I analyse the attached circuit?
Especially in the red markings...
For example the divided voltages or the current flows in the circuit...
Thank for your help in advance.
Hi,
To get a basic idea what is going on you have to assume some input capacitance of the CMOS gate. Then solve for the points where the diodes turn on and turn off, then calculate the charge time of the input to the CMOS gate.
This circuit looks like some sort of delay circuit where they want to generate a delay for the high going edge of the input signal. Only for the high going edge because D2 and Rb create an asymmetrical drive for the CMOS gate.
The zener could be there to help perform a level conversion or just protection in case the input goes too high for some reason, including a spike on the line.
D1 is a little less clear, but may be there to provide fast spike protection.
So the way to start the analysis would be to assume the input is zero, then calculate the different voltages, then allow the input to go high, then calculate the voltages again. Since the voltage of the battery is not given, you might consider three different possibilities and analyze for each case separately:
1. Battery voltage is less than the CMOS gate power supply.
2. Battery voltage is more than the CMOS gate power supply.
3. Battery voltage is equal to the CMOS gate power supply.
All the while you have to consider the possible threshold voltages for the SMOS Schmitt Trigger input as well as the input capacitance.
You might get different results for each case especially for certain battery voltages.