electronics
posted by dale mckinney .
which of the following statements is a true statement concerning the TN theorem? #1the TN theorem can be applied only to dc circuit analysis. #2the Tn theorem can be applied only to ac circuit analysis #3the TN theorem can be applied to circuits containing both dc and ac sources
#4the TN theorem can be applied to both dc and ac circuit analysis as long as the circuit contains either all dc or all ac sources

Well, I Googled TN theorem and can find no mention of anything with that name, except for your question.
Does it have anything to do with Thevenin's and Norton's theorems? 
yes

In that case, #3.

Here we examine noise in a digital channel between an AND gate and an inverter shown in Figure 16. The channel has a length of D=30m and noise is added in at the rate of 0.6Vm.
To correct for that noise, we introduce noninverting buffers into the channel. The purpose of a buffer is to take an input and replicate it at the buffer's output. This buffer is useful because it clean up a signal which no longer meets the ouptut specification of the static discipline due to noise, so that it once again meets the output specifications of the static discipline.
These buffers, as well as the gates shown, obey the following static discipline: VOL=0.7V,VIL=2.0V,VIH=3.0V,VOH=4.3V. What is the minimum number of buffers required to connect between the digital links in order to ensure correct operation?
Now let's consider the NOR gate in Figure 18 which has VS=5V and the following given static discipline: VOL=0.9V,VIL=2.4V,VIH=3.5V,VOH=4V.
Assume that both MOSFETs have the same VT and RON=20kÙ.
What is the minimum value of VT in Volts that allows the NOR gate to satisfy the given static discipline? (This is 2.4)
What is the maximum value of VT in Volts that allows the NOR gate to satisfy the given static discipline? (This is 3.5)
What is the minimum value of RL (in kÙ) that allows the NOR gate to satisfy the given static discipline? ?????