Questions tagged [circuit-design]

a term to describe how a circuit should behaved based on accomplishing a particular task. When designing circuits, one should consider how it works, the target specifications, efficiency, cost effective, code compliant, and ethics.

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25 views

Circuit for reversible motor controlled using relays

I am very new to electronics and drawing isn't my strength either, so please forgive the bad diagram. But I hope it makes sense. I want to be able to control a motor using relays and be able to ...
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1answer
37 views

Visual example of PNP transistor

Following this question, Visual example of NPN transistor, is the following a correct understanding of a PNP transistor? To be honest, I have no idea why the top of the transistor (where the current ...
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1answer
70 views

Visual example of NPN transistor

Is the following a correct understanding of an NPN transistor? Basically, a positive voltage source needs to flow through the Base of an NPN transistor and out through the Emitter, so it needs to ...
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0answers
78 views

Is it OK to have flying leads on a differential pair?

I'm designing a small daughterboard that contains a microcontroller and a USB port. This board also has a connector to allow it to connect to a motherboard. What I'd like to be able to do is to have ...
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4answers
114 views

Best way to drop 10volts at 0.25A with linear regulator?

What would be a minimalistic circuit design to convert 14V to 3.3V at 0.25A with a linear regulator? I'm thinking about two linear regulators. I've tried LM7805(14V-5V) to LD1117(5V-3.3V.) LM7805 ...
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3answers
85 views

Grounding for a battery

Given a 9V battery as the only voltage source for a circuit, where is the Ground usually put? Is there a standard, for example, that puts the negative terminal at 0 and the positive at +9? Does it ...
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5answers
16k views

Difference between the following two very basic circuits

What is the difference between the below two circuits? I know the bottom circuit has 'ground', but what does that mean exactly? Why would someone want to construct the second circuit over the first? ...
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2answers
67 views

Wiring colors for 'intermediate' connections [closed]

It seems to that red is the color usually used to connect to the positive terminal and black is usually used to connect to the negative terminal. However, I have seen numerous other colors as '...
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3answers
60 views

Phase Detector for PLL: Operation and Realization

I have some doubts about the realization and the operation of a phase detector for a PLL. My reference book is "The Design of CMOS Radio-Frequency Integrated Circuits" (Thomas H. Lee). The basic ...
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1answer
70 views

Kicad Eeschema window does not respond when opened in windows 10 (Not working)

I have just started with Kicad. Never used it before. I downloaded and installed kicad, opened it, created a new project. Everything is fine until that point. But when I open Eeschema window for ...
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0answers
40 views

IN: 5.5-110V, OUT: 5V, 3A max buck converter

I'm looking for a DC to DC converter with the following characteristics: Input voltage: 5.5 to 110V Output voltage: 5V+-0.2 Output power: 3A It is required for a ...
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1answer
52 views

Determining values to convert square wave to sine wave at low frequency

For a project I am working on, I have a 1Hz square wave coming from a real time clock, and need to convert it into a sinusoidal wave to pulse LEDs. After some googling and playing around with ...
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69 views

Basic circuits to understand transistor [closed]

I am trying to understand how transistors work, and I'm having a difficult time finding some circuits to show a very basic way in which they work. For example, the following circuit helps me ...
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1answer
74 views

In this circuit, why the first capacitor cannot be “open”? [closed]

In this picture, you can find first capacitor and i did simulation by using matlab simulink and then i measured the current flow to the first and second capacitors. i think that capacitor will be ...
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1answer
61 views

Advantages of using active inductors in ICs

I have seen that there exist many methods to realize equivalent inductors in IC through active components. For instance, through gyrators realized with Op-Amp. This solution will require a lot of ...
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1answer
50 views

IR emitter to keep TV on

We installed some TVs in the main floor of our facility. We have personnel here from 8am until 12am, and the TVs have been set to turn on at 7am and off at 1am. Sometime during the day, YouTubeTV asks ...
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1answer
54 views

DC Wiring Color Conventions

Below is a simplified version of a system I'm working on. There's over 10 devices and they all come through the ammeter and split off into each device (only using 2 devices here for simplicity). The ...
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2answers
64 views

Positive and negative rail for op amp circuit

I need a positive and negative rail to power an op amp Since it's an op amp for a voltage reference, would using a circuit like this one be enough? Input voltage is unregulated 37 volts, with 4.7k ...
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1answer
39 views

Which parameter to use to specify the relay in a CAN line communication?

I need to use SSRs (solid state relays) to comute lines of comunication to a vehicular OBD-II interface. I will use SSRs to choose wich lines will be used at the pins of the connector. The lines wil ...
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0answers
46 views

Clipping circuit with zeners grounded? [closed]

Is there an advantage to grounding the zener diodes in a clipping circuit as opposed to just connecting them together? This would be for a differential signal so both the pos and neg sides would need ...
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1answer
44 views

Circuit to find difference, in binary, between most significant and least significant 1

If A = 1100, and B = 1010, I want to find the positional difference between the first 1 from the left on A, and first 1 from the right on B. In this case the answer would be 10. In other words, the ...
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1answer
39 views

Calculation of a feedback resistor in an inverting shmitt trigger

This is taken from a frequency counter circuit based on a schmitt trigger comparator . The frequency counter has a noisy immunity threshold of 100mV. How would you calculate the Rfeedback resistor ...
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3answers
93 views

Is it possible to design a dynamical/adaptable functionally/logically complete circuit?

Biologist here but I've been reading about functional completeness in digital logic and I am wondering if there is a universally complete circuit that can be modified to express any boolean function ...
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1answer
87 views

Transistor audio amplifier with dual voltage supply

There are lots of similar topics, but I can't find answer that will satisfy me. So, basically I am trying to do a transistor audio amplifier with dual voltage supply (+/-12V). I found circuit like ...
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1answer
65 views

How to measure Johnson Noise precisely experimentally?

I want measure Johnson Noise across a resistor having certain over the certain range of frequency or bandwidth practically. I am starting from scratch, how can I build circuitry and instrumentation so ...
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3answers
100 views

What is the rule to put grounding in the circuit schematic, and what is that grounding for?

Already so many discussions about grounding. But the more I read, the more I got confuse as there are many disputes. The above are cases where grounding are quite confusing. Grounding or earthing, I ...
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3answers
121 views

Differential Pairs and GND

I have some doubts about different configurations of differential pair I have seen in many cases: In these schemes, biasing network for the gate is not shown for simplicity. All of them are excited ...
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2answers
78 views

Noise on stereo summing circuit from LED's

I've been a tinkerer and hobbyist for 20 years now, but mostly in software. I've done my fair share of simple soldering (replaced controller ports on an original Xbox with actual USB ports, for ...
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4answers
173 views

How do computers power so many lights on a keyboard?

Beginner here. I am working on building my own keyboard PCB, and I wanted to add a backlight for my keys. However, I've been reading methods of powering teensy little 3mm LEDs and it seems like an ...
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1answer
57 views

A simple way to test op amps

I built this small circuit to test if the op amp is working; or if I understand how they should work. I don't have a bench power supply so I take the 7 voltage that I have, I used a resistor divider ...
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3answers
98 views

Do I need additional power for an IR LED diode 50 feet away from a Raspberry Pi?

I'm creating a central remote to control my mini-split HVAC units. Those units are controlled with an IR remote. Each unit is in a different room of my house. I have everything working on my ...
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1answer
31 views

swapping a louder siren into circuit?

I bought an inexpensive battery-operated door alarm that works using a reed switch and sounds a small buzzer when triggered. To beef it up, I'd like to swap in a louder separate siren/strobe light to ...
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0answers
41 views

Is there a way to visibly measure charge on CR2 battery?

I have a CR2 battery I’m using in a project. It is buried away in the housing and without opening everything up, I’d like to find a way to somehow measure the current charge on the battery from the ...
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0answers
36 views

Which type of components required to achieve pre-determined output sequence?

Just getting back into electronics. I would like to create a circuit that can be programmed to control the state of a light bulb / relay - e.g., on for 2 seconds, off for 12 seconds, on for 5 seconds, ...
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3answers
92 views

Discrete linear voltage regulator

I am trying to make a discrete component linear power supply. This schematic seemingly works but it doesn't work when I build it on my breadboard. I am taking 110 volts through a transformer down to ...
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0answers
51 views

Designing MOSFET bridge rectifiers for high voltages

I've been looking into MOSFET bridge rectifiers, also known as "zero IQ" rectifiers, as a replacement for traditional diode-based bridge rectifiers. Here's a simple example: The benefit, of course, ...
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1answer
31 views

Double DC Motor Compressor Circuit Protection

I'm a mechanic! So, please do not blame me for stupid questions. I did a lot of research using relays for switching DC motors. The following circuit is showing the current version I want to realize ...
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4answers
55 views

Polarization of Radio-Frequency Low-Noise Amplifier

I was reading the chapter about Low Noise Amplifiers from the book "The design of cmos radio-frequency integrated circuits" by Lee, and I have seen this example: I do not understand the part inside ...
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0answers
72 views

How does this circuit protect against reverse polarity?

I'm looking at the datasheet for the VND7004AY high side automotive switch. The diagram below shows the internal structure of the device and claims it is protected against reverse polarity. I have 2 ...
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1answer
50 views

How to properly wire a 4.5V LED strip with 12V motors

I'm modding a Nerf gun (Rapidstrike to be exact), and I put a 3S Lipo in there with 1000 mAh. The circuit right now is a rev switch, trigger switch, switch behind the pusher, battery, pusher motors, ...
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3answers
129 views

Buck Converter Feedback Circuitry

Recently I have been studying feedback in switching power converters, and one thing that is still a bit confusing to me is the way the error amplifier is implemented. Here is what the control diagram ...
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2answers
74 views

A logic circuit with a NOT condition

I have the following problem to solve and Im a bit confused: I have a ceramic factory that is based on a circuit with 4 outputs: timer that outputs "1" when the oven is on (timer) sensor that ...
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1answer
96 views

5A constant current/ constant voltage using LM350

I take the circuit below given in a TI application note, and I have some questions about the way the circuit works: The circuit is designed as a 5A constant current/constant voltage regulator. First ...
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1answer
71 views

Thermal Noise in Oscillators

let's consider this circuital model for an LC oscillator in which the parasitic resistance R is affected by thermal noise (represented here with an equivalent noise current source, according to the ...
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1answer
42 views

Counter Circuit starts from wrong number in Logisim

I'm trying to design a synchronous counter using J-K, T and D flip flop. It should count as "1, 3, 0, 2, 7" and 1 respectively. Everything works fine, i designed flip-flop tables and input-outputs ...
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1answer
39 views

How many unused inputs are there in a BCD adder?

My book provides this BCD adder with the truth table: Since this is meant to add number in BCD there are combinations that aren't going to be used. My book asks to calculate how many of such ...
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1answer
17 views

Effect of lower voltage supply in flash circuits

Let's consider this circuit which represents the internal structure of a flash for a generic camera. enter link description here Here my reference guide. Usually in an external flash there are 4 ...
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3answers
103 views

Basic understanding of Voltage drop

What is the second/lower 15 k-ohm resistor for? I understand why there is a 12 k-Ohm resistor in the top, that's for the V-out. But why is there a 15 k-Ohm resistor in the lower right? Why would you ...
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2answers
61 views

Frequency Domain Analysis with Transistors

I have some doubts about how some circuits with transistors are described in electronics textbooks. Let's see an example (taken from Thomas H.Lee, The Design of CMOS Radio-Frequency Circuits). This ...
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3answers
54 views

How to choose the appropiate analog power supply filter inductor

I'm currently studying designs for a pulse oximeter for use with Arduino, I have seen two Schematic designs form the same company, https://www.protocentral.com/sensors/1113-protocentral-afe4490-pulse-...