# Questions tagged [circuit-analysis]

Circuit (Network) analysis is the process of finding the voltages across, and the currents through, every component in the network.

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290 views

### Why can you define closed loop gain when return ratio approaches infinity like this?

This is from this lecture video. Please check the video link if you're not familiar with the terms. I can explain it but I think the video lecture is pretty good at it. Because the feedback amplifier ...
388 views

### Switching the high side of a load - The Art of Electronics

I am going through The Art of Electronics Third Edition. There is a note 12 unter Figure 2.10. Why Q3 would not switch if R3 = 100 Ohm?
50 views

### Can we look at only the voltage specification of a product? [duplicate]

I saw this specification in the product I wish to buy. Does that mean if I connect a 12V voltage supply from a battery, the current will actually be 5.8 A by default since the resistance of the device ...
190 views

### Understanding battery protection IC

I'm trying to understand an IC for battery protection, code HY2111 (datasheet) The internals are: And usage example is: My doubt is the part of the over-current protection. How this circuit is able ...
69 views

### Forward bias or reverse bias

What do we take, the flow direction of electronic current or conventional current through a diode if forward bias?
134 views

### Please help me understand the reason for using this 5V battery and 2k resistor at the gate of this MOSFET

Please help me understand what that V3 source and 2k resistor are doing here. The output from the comparator U4 will form the gate voltage of MOSFET. Because of the 2k resistor, the voltage at the ...
95 views

### Is there any way to simplify this circuit? [closed]

I am trying to get the Voltage across R2, R5. Could someone explain with detailed steps? Thanks
578 views

### Does the electric potential of a closed-loop circuit maintain a constant value?

This question is related to the electric potential of a circuit point, not the voltage between two points. Here is a sample circuit diagram with $V_{circuit}=5V$ and $R_{circuit}=5 \Omega$. If ...
28 views

### How can I relate input voltage, load voltage and reflection factor r?

I am given a circuit as given below. I have to find the relation between $U_2$ , $U_1$ and $r_a$ (reflection factor). I couldn't find the expression containing only these three terms as given ...
119 views

### Thevenin equivalent or mesh-current in a diode circuit

I've been stuck on a problem for a couple days and many hours now and see no other option than to ask here and see if you can help me or give me a lead. What I have been stuck on is this: My initial ...
35 views

### Tradeoff between (op) amplifier voltage range and offset and settling

I know that an amplifier (let's take an op-amp) can't swing rail-to-rail. The reason has to do with the load device. For example, in a normal common gate/common base amplifier, the load device causes ...
95 views

### Jump in RC current response to a square wave

Periodic square wave feeding an RC circuit: I am currently studying RC filter response to a square wave input with a period of $T_1 + T_2$. I have understood about voltage expressions and current ...
86 views

### Reason for using small sampling resistors in voltage measurement circuits

The above schematic is of the ZMPT101B module (current type voltage transformer) collected from Arduino Forum. All of the modules available in the market use a similar type of circuit having two ...
49 views

### RL Transient Analysis confusion

simulate this circuit – Schematic created using CircuitLab When I am using Thevenin's circuit and deriving inductor currents equations i am getting different Time constant $\tau$ from what I ...
38 views

### Power delivery, purpose of capacitor? [duplicate]

I see this circuit design a lot in systems that require a sensor, a microcontroller, or other devices to be powered (with 5V for example). In the attached diagram, if V1 is my power source supplying ...
211 views

### What is the small signal gain for this circuit?

The question looked easy at the first sight. I found the quiescent current through the BJTs. I can say that |Vbe| = 0.7 V for both BJTs. Therefore, current through 1 kΩ below Q1 = 2 mA. Similarly, ...
82 views

### ESP12E : GPIO01 & GPIO02 Usage

I'm making a circuit for driving Relays, LED's from push button and few other functionalities from ESP12E module. for which I'm using simple Transistor driving circuits as shown in image. In this I'm ...
122 views

### How to calculate the real output voltage of a rectifier circuit (center tapped rectifier)

In my class, we are using Proteus 8 to simulate simple rectifier circuits. We are not familiar with analog electronics yet. Since the class is all about using engineering software, there are not many ...
94 views

### How to write transfer function is s-plane of single bridge rectifier?

I am trying to write a transfer function of single phase rectifier so I can use in Matlab to look for phase margin and gain margin: here an example I took from Circuit-lab I could write the transfer ...
44 views

### Modelling ESR of a parallel plate capacitor

I am trying to model a parallel plate capacitor (on die capacitor generated using metal plates.) I know the capacitance per unit area, and metal sheet resistance. No knowledge of the dielectric. I ...
95 views

### I am struggling to understand how to show the cut-off frequency

I understand that the cut-off frequency f = 1/(2πRC) or 70.7% from the maximum. The issue I have is I don't understand how these end up being 2 different points on my graph. Above is the cut-off ...
45 views

### Changing regular momentary switch to a motion detector in staircase timer circuit

(Reference image below) I have a classic staircase timer circuit ("TC") where any of the momentary switches will trigger the timer to power all the bulbs. Now I want to replace one of the &...
756 views

### How can I solve this simple BJT circuit?

Looking at this circuit (first circuit): Choose a value for V2 between 0V and 10V. Then how could we know the IB, IC, IE, VB, VC, VE? Can we solve it by hand (by hand means the value IB, IC, IE, VB, ...
58 views

### Test Input Transformer with Signal Generator

I have an RF Amplifier kit that is not working. The main problem is that the input transformer presents the radio with a high, unexpected SWR. It does amplify, so something works. The transformer is ...
103 views

### LEDs combinational circuit series and parallel

I have a project involving lighting up 12 dual LEDs using a 9-Volt DC Power Adapter with Max current of 500 mA According to the datasheet Dual LEDs datasheet the forward voltage is about 2 V at 20 mA. ...
35 views

### Wilkinson Divider with one shorted and open port

I have the following setup: It is my task to calculate the only value ($S_{11}$) of the scattering-matrix of the resulting one-port. Here is my idea on how to do that: From the left port and ...
96 views

### What would be the Open Circuit Voltage and Thevenin Resistance in this Circuit?

I am hoping someone can help me understand Open Circuit voltage and Thevenin Resistance. To test my understanding I created the attached circuit and ran a transient analysis using LTSpice. With a ...
418 views

### How do you divide gain for the first and second stages of the two stage opamp?

For this two stage opamp, how would you divide the gain for the first and second stage? For example the target gain is 2000 V/V, then you would have many option to divide the gain like 45/45, 30/70, ...
44 views

### Calculating N-type enhanced MOSFET gain with two different equations brings me a different result?

Hi, take a look at this problem from my notebook. Leave alone the fact that the resistor should actually be 1,111.111, it is not related. If they claim that VGS=2 and Vs is connected to ground it ...
75 views

### Joining two parallel branches with a wire

In the above circuit (grounding the negative terminal of the battery,) will the potential at C and D be the same? According to my physics teacher, the potential is the same at the two points. Why is ...
32 views

### Help understanding current sense application note to inject feedback into buck converter

I am trying to understand this application note using MAX4173H to inject feedback into a MAX1692 step-down converter. How to they determine the precise point at which the current limit will kick in, ...
75 views

### Super weird multimeter behavior, multimeter is jump starting circuit

So I have a custom PCB for a project that has an output port for a pump. The pump is rated for 8-24 VDC, 3-35 W, .3-1.5 A. The starting voltage is 9-13.2 VDC. The PCB is powered by a 24V power supply. ...
104 views

### Analysis of DC-DC converter with bidirectional power flow

Let's assume that Vin is a DC battery and Vout is a spacecraft main power bus. It is given that this circuit is DC-DC converter with bidirectional power flow. But to me this circuit exactly looks like ...
133 views

### What is the op-amp output voltage for a voltage-controlled current source?

I am trying to analyse the voltages in a voltage-controlled current source. What I have so far: Vin = V_C V_B = Vsupply - I_shunt*R_load However, I don’t know how to find an equation for the op amp’...
88 views

### Help with AC analysis

Can someone help me solve this? The answer is at the top right: This is what I tried; can someone show me what is wrong?
40 views

### How to block DC offset voltage on a potentiostat output?

I have an AUTOLAB potentiostat: working electrode (WE, Pt wire), counter electrode (CE, Pt wire), reference electrode (RE, Ag/AgCl solid state). I would like to capacitively couple the potentiostat ...
111 views

### What is this binocular transformer and how do I model it in LTSPice, Have High SWR In Ham Radio

I purchased this 70 Watt Amplifier Kit and built it. Unfortunately, the kits do not come with any instructions. I have managed to find a variety of web sites where people built the amp and offered ...
53 views

### Why I am seeing small voltage in the voltage display from detector?

I am using this detector to detect the brightness of an LED (powered and controlled by controller). When I use this multimeter to measure the detector output, I see the range of detector from 0-12.13V....
114 views

### Difference between unbalance load connected to grid vs isolated generator

Given two cases as following- CASE 1 An isolated 3-phase synchronous generator in star connected to a star-star 3-phase transformer and then secondary of transformer is connected to a highly unbalance ...
66 views

### Weird result when finding ripple bounds of RC circuit with square wave input

If $V_{ext}$ is applied to a RC circuit, then voltage across capacitor is given by: $$v(t) = V_{ext} + (V_i -V_{ext})e^{-t/RC}$$ Using above to find the ripple bounds $v_l$ and $v_h$, get two ...
100 views

### Why is $V_{\text{ov}}$ not a good design parameter?

Can anyone explain why $V_{\text{ov}}$ is not a good design parameter here? I understand why $C_{\text{gs}}$ is bigger (low bandwidth), but still can't understand the conclusion they made. Source:...
117 views

### Why is $V_o=-V_c$ in this circuit?

Why is $V_o=-V_c$ in this circuit? Is it a derivation from Kirchhoff's voltage law? simulate this circuit – Schematic created using CircuitLab
1k views

### How to handle four resistors in a square (OP-amp)?

I want to analyze this circuit and find $\frac{V_{out}}{V_{in}}$. But how should I handle the four resistors in the square? simulate this circuit – Schematic created using CircuitLab Can I ...
101 views

### Is there any straightforward simplification for the attached DC-Circuit

Simplifying a DC circuit would start by collecting the parallel resistors or the ones in series, for this circuit, I do not see any simplification, Am I right? My end goal is to calculate the values ...
182 views

### Component identification - Power supply circuit component exploded

I am fixing the power supply board of a big mobile sound system. Skytec PA-200 - sadly I could not find any schematics or more information on it. Unfortunately not only an electrolyte capacitor but ...
134 views

### Trouble Understanding Dual Transistor Flashing Circuit [closed]

I am having trouble understanding how this circuit works. I've breadboarded it out and the LED flashes but I can't seem to wrap my head around how the NPN vs the PNP is creating the flash. Any help is ...
53 views

### Thévenin Equivalent in a Circuit

I came up with the following problem that asks to find the Thévenin equivalent of the circuit below. However in the manual solution, I found that the author uses 1A for the a to b branch, and I have ...
41 views

### Reading button state of self holding is high all the time

I have a self-holding circuit for a push button that is used as the power button for a 7.4 V supply. The button state should be read by a PI4IOE5V9539 port expander....
I decided to calculate the input impedance of the following emitter follower circuit as a practice. I used this well-known small signal model for the BJT: For voltage gain, I obtained A_\text{v}=\...