I know this is an extremely trivial question especially after studying thus far, however, I still can't wrap my head around how we are supposed to calculate the nodal voltage depicted below: enter image description here

In this case B, I am supposed to figure out whether or not the diode D2 with a threshold voltage of 1V is activated. In order for it to be so, the voltage across the diode must be greater than 1V. In a simple series series circuit B would obviously be 0V but I can't figure out the voltage of B in this circuit to see whether or not D2 is active or not. I know ohm's law cannot be used here, any help is appreciated. Would B just simply be 2V because the resistor only limits current?

  • \$\begingroup\$ If you think to use nodal analysis , think again! \$\endgroup\$
    – Miss Mulan
    Sep 21, 2021 at 19:37
  • \$\begingroup\$ Because the V1 is lower than V2. You need to determine the voltage at point A first. We can see that the voltage at point A (D1 off) will be around 3V if D1 is the ideal diode or 2.5V if D1 Vf =1V . Therefore there is no way for the D2 diode to conduct any current . \$\endgroup\$
    – G36
    Sep 21, 2021 at 19:38

1 Answer 1


First consider the circuit with V1 disconnected, then you can calculate the Voltage at A. If adding V2 results in a forward voltage existing on D2 then D2 will allow current to flow. Once you know whether or not D2 is conducting, you can recalculate the voltage ms and currents.


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