Discussion in 'Homework Help' started by ramphisaj, Feb 23, 2007.
i need help please see attachment.
Is it possible that each of of the two circuits in question have a resistor between the junction of the diodes and the positive supply input?
If not, then the circuits as drawn, while doable, are not very realistic.
There is bound to be a diode or diodes destroyed in the circuits as drawn.
IF you have rendered the schematics for this problem correctly, then I feel sorry for you, because it is a foolish scenario/question.
Assuming the diodes could somehow handle the current due to the voltage potentials, the answers are:
Because Vout is tied directly to the supply voltage(s) -- especially after the diodes burn up.
I think your circuit needs a resistor between +5V and output. Then (and only then), this represents some form of diode logic circuit. In the first circuit (if a resistor is inserted between +5V and out), and assuming a volt drop of 0,7 volts per diode, the two diodes with +5V inputs will not be biassed at all and will have no effect, however, the two diodes with the -5V inputs will be forward biased. The output will then be 0,7V higher than the -5V, i.e. -4,3V.