My apologies for another blog on this subject, I take the test again tomorrow.
1. OpAmp Circuit.
(R2/R1)*Vin = (100k ohms/10k ohms)(0.01 V) = 0.1 V now, I'm just confused from then on, I know how to solve it as such, is it because from the R2 it was 0V, and it's 0V - 0.1 = -0.1 V as Vo? I is V/R(in this case, R0?) so (0.1 V)/(100 ohm)
1B. Another example:
How the heck do I even start this? It was something I just created.
1C.
Would the [+] be included or ignored, if there was a resistor value of it and a V2 input?
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2. BJT Grr!
Sorry about the question marks, they're supposed to be Kohm symbols, anyway.
Since V2 is 9v, it goes down and has to go to the Vo, I understand that, and Vp is 0.7V.
9V - 0.7V 8.3V now. And since I know current, i, it is provided and it's 2 mA through diode, V = IR, thus: V = (0.002)(1000 ohms) 1k from R2 so that's 2.
8.3V - 2V = 6.3V, this is c, however, for V1 and R1, this isn't included, may I ask why? Even though V1 has no value, R1 is 10k ohms.
In advance, thanks for looking.
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1a. The voltage above Ro is simply Vo, so as soon as you figure out Vo, the current you get through Ro is just an application of I = V/R. In other words, once you find Vo, everything else but Vo and Ro is irrelevant to you. It doesn't matter what voltage path you trace to get to that point; the answer, which you already determined, says that Vo = whatever you solved it to be.
1b. Uh a quick check at wiki tells me the inputs to an ideal op amp (in reality there's always current leakage of some sort) have zero current flowing through them, so that 2000 ohm resistor you've got doesn't matter. It's interesting to note that because you've got ground connected to V+ and V- of the op amp (trace direct path from ground through wires to V+, ground through a resistor with no current to V-), V+ and V- will both be 0! So you're getting no gain. Vo = 0. 
1c. V+ is again 0 no matter what the input to the left of it is, because of the ground you put there. For V- do the usual for solving that (same as 1a).
2. For the npn BJT, V1 and R1 don't matter because you are given the current through R2. Were you not given this current, you would need to know V1 and R1 in order to derive current-voltage relationships for the BJT (I'm assuming you studied some kind of small-signal model for these things, like the hybrid-pi or h-parameter?). This would make the problem several steps longer instead of really really short.
For the h-parameter model, H_FE is the current gain (also commonly referred to as beta). This is related in the following equation for the forward active mode of bias:
(base current) times (H_FE) = (collector current)
(Ib)(HFE) = Ic
In the npn BJT in this circuit, the base is the left side and the collector is the top (emitter is bottom). You would have to check if it's in forward active mode by seeing that the base to emitter voltage is sufficiently forward biased enough (otherwise you're in cutoff) and the base to collector voltage is sufficiently reverse biased (otherwise you're in saturation). Etc. etc. etc. more details. Just throwing out some key words in case you remember any.
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EPT![[image loading]](http://i28.tinypic.com/qohxkg.jpg)
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