# Tagged Questions

65 views

### Nodal analysis in simple circuit

I have a circuit to solve: In this approach, I inferred the V1 from the parallel connection of voltage source. For the second node, I have applied the KCL. I also tried to do it another way, by ...
154 views

### Will a 6 volt LED kill a 9 volt battery quickly?

I am building a little circuit and I am adding a little 6 volt LED to tell me when I have power going through. But my power source is a little 9 volt battery, will this LED kill this battery quickly? ...
61 views

### What does negative impedance mean in the context of miller's theorem

Miller's theorem states that for a linear circuit of two nodes with voltages $$V_1,V_2$$ which are connected by an impedance, $$Z$$in series, circuit could be represented by an equivalent one with ...
117 views

### What is Kirchhoff's voltage law all about?

what is the Kirchhoff voltage law ? isnt it the sum of potential drops as we move along a circuit till the same point should be zero it is simply energy conservation law that when the battery ...
60 views

### What are the differences between Channel-to-Ground & Channel-to-Channel isolation?

I have the following questions regarding different types of isolation techniques: What are the major differences between Channel-to-Ground & Channel-to-Channel isolation techniques? Are all ...
164 views

### 4,5V 650nm laser, will I need a driver?

I just bought a package of 100 laser diodes on eBay: http://www.ebay.com/itm/110887381932?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 My first question is: Will they need a driver? ...
236 views

### Trouble on switching a 3V relay with Arduino digital pins

I am using the Arduino Ethernet with POE and I am in trouble when I have to enable my relay by using a digital pin. What I would like to make is to start a motor by using a relay, which relay is ...
490 views

### Extracting the Square Root of a Voltage

I'm trying to discover a circuit that will produce a voltage which is some factor of the square root of the input voltage. I.e. $V_{out}(t) = K\sqrt{V_{in}(t)}$. The factor K is irrelevant. I ...
84 views

### Choosing the right batteries

I have a Radio control circuit for a boat I made and I don't really know which kind of batteries I have to use. Can someone explain me the differences (A, AA, AAA, C, D) and others if there are) and ...
281 views

### Drop USB voltage to 4.5v

I have different 4.5v small LED circuits (from 100mA up to 350mA consumption, with some 555 ICs) that I'd like to power using a small regulated USB wall charger (4.95V output, 0.8A). As per my ...
65 views

### Small-signal input and output resistances of the circuit

I am given this circuit: And I am trying to determine the small-signal input and output resistances. I was either given or found all the following info for the circuit: VA = 110V β = 115 T = ...
173 views

### Is it possible to provide power using (effectively) a single wire?

I come to this question after a few thoughts on capacitors. A capacitor essentially transfers (and stores) energy using an electric field through an insulator. The plates of a capacitor are not ...
76 views

### How to find τ in these circuits?

I know that $τ = \frac{L}{R}$, but what is $R$ in this formula? It seems to be the total resistance, but how to find it in the schematics?
464 views

### threshold problem on a Schmitt trigger op amp

I have the Schmitt trigger op amp on the below diagram. (channel A & B refers the oscilloscope probes on the following figures). The resistor values are selected to set the trigger threshold as ...
250 views

### connection from an comparator to an optocoupler

I have the circuit below to decode a signal that is defined as Logic high >9.5 V and Logic low <6 V To determine the ...
168 views

### Voltage drop from poor connection

In a DC circuit, why does an open circuit voltage drop appear across a bad connection? For example i have 48vdc wires where a connector is charred from bouncing/bad contact. Under no load the side of ...
95 views

### Mosfet Circuits Voltage

So let's take a simple cmos circuit like this: So I get that for DC analysis $V_G = 12 \frac{R_2}{R_1+R_2}$ and then $V_{GS}$ makes sense to me...because there is a constant $V_G$ value ...
156 views

### Serial and parallel circuits and power

If I have 12V of power, and wanted to power LEDs with a forward voltage of 2V, could I only power 6 of them? Would I connect the cathode of one to the anode of the next, creating a kind of serial ...
197 views

### Circuit analysis with nodal analysis

[EDIT] I'm going to give mesh analysis another go, and see where that gets me. [DOUBLE EDIT] Mesh analysis didn't get me anywhere :( Im tearing my hair out over this problem, so any help would be ...
135 views

### What is the voltage at a node between two series voltage sources?

Hopefully the title explains it. As an example, what is the voltage at node one in the schematic below? And more importantly, why? I believe the answer is 0V, but I suppose what I'm thinking is: Why ...
216 views

### Simple circuit Voltage regulator question?

I am trying to build a simple circuit that takes a 9v battery through a voltage regulator that outputs 1.5v across a load resistor . The load will be just a piece of metal that gets heated up. My ...
399 views

### Parallel and Series Circuits Question (Electron Flow)

So this is a pretty basic question, I understand the aspects of parallel and series circuits but don't understand why? For instance: How can the Battery be "drained" faster when say 3 LEDS are ...
1k views

### How do I calculate the gain of an op-amp summing amplifier?

So if I have a summing amplifier circuit like the one below: I know the Vin1, Vin2, and Vout value and the circuit is designed such that Vout = -(Vin1+2Vin2) but how do I calculate the gain? I know ...
128 views

### How do I calculate the voltage at these locations?

I'm wondering how to calculate the voltage on the following charts (series circuit and parallel circuit). I'm interested in the math process involved, not the answer. I'm mostly confused about how ...
568 views

### How to remove 20MHz SPI signal noise?

I did some SPI software configuration for my DSP board. Then I soldered several missing 0 ohm resistors onto the board so I can tapping the SPI signal from pin headers. Then I measured the SPI Chip ...
659 views

### Where exactly do the electrons go in the circuit once they traverse the circuit elements?

From my understanding, when a voltage is applied to a circuit the free electrons in the circuit elements start moving towards the higher voltage potential. So what happens once the electrons reach the ...
1k views

### Why is the voltage across a reverse biased diode equal to source voltage?

Why is it not equal to zero since a reverse biases diode is essentially an open circuit?
633 views

### What is meant by relative voltage?

Suppose you have a circuit ,you are told that the voltage at point 2 relative to point 1 is -90V, the voltage across R2 is -30V and V0 is 200V. What is the meaning of voltage at 2 relative to 1? ...
213 views

### What's passive about the passive sign convetion?

I've heard and read about the passive sign convention, but don't really understand its meaning and importance in solving electric circuits. Is this because of conventional current which flows ...
745 views

### MOSFET Switch w/ Fast Settle Time for Switching E-Field

Application: I have a copper mesh (10cm x 10cm square) in a vacuum chamber connected to a BNC connector by a 24-cm-long copper wire. The goal is to switch the mesh voltage (referenced to ground) from ...
88 views

### which battery will supply the load?

I have connected 14V supply terminal from alternator to 12V battery terminal and has taken the load across these terminals . But the load is operating still in 12V, and when measured across the ...
324 views

### MOSFET sub-threshold operation

I have a question related to the sub-threshold operation of MOSFETS. Let's say I have the following setup: How can I calculate the sub-threshold current ( Id when Vgs < Vgs(th) ) at Vgs = 0.5V ...
243 views

### what is the magnitude of total voltage in the below circuit?

I was working on some RLC circuits and I found a question something like this. In series RL circuit, $V_R$ = 4V and $V_L$ = 3V. what is the magnitude of total voltage ? I just thought $V_T$ = ...
236 views

### Thevenin Resistance?

I don't understand our professor's explanation for the answer to this problem: An LED is connected in series to a 150ohms pull up resistor and a MOSFET with drain-source resistance of 3ohms. The Pull ...
354 views

### Simple voltage divider question

So two resistors in series can be a voltage divider. So say I have the following circuit - From what I have read the voltage gets split across the resistors based on their resistance. So there will ...
I am trying to calculate the voltage $Vw$ of the following circuit: I have little experience with these kind of problems, so I tried to solve first a more simple circuit that did not include the ...