# Questions tagged [active-components]

Components which provide a gain in the circuit where they are applied. Typical examples are transistors and op-amps.

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### Capacitors and batteries as active/passive components

I'm trying to better understand the concept of active and passive components, mainly with respect to capacitors and batteries. I found that - according to Wikipedia - there are two definitions of ...
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### Mistake in using KVL and KCL in ideal opamp-circuit

I have the following circuit: simulate this circuit – Schematic created using CircuitLab And I used KCL and KVL to write the following sets of equations:  \begin{cases} \text{I}_0=\text{I}_1+\...
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### Is a transistor truly an amplifier?

My understanding of transistor is that in it a tiny current controls a huge current. I get that concept. If that is the case, it is not amplifying anything in my opinion. Sure it does dictate when ...
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### Is the Gate-Controlled Diode an instance of a trancitor?

I'm not sure it entirely counts. It certainly isn't useful in the way that the current-controlled voltage source is useful as the original transcitor paper describes, but more importantly, I am unsure ...
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### PLCC4 footprint how to connect LED

I am confused as to how I should be connecting this design since this LED LTW-E670DS since it has 4 pins. How do I connect it? Pin 2 is Anode and 1 Cathode but 3 and 4?
249 views

### Why can you measure input and output impedance of a amplifier circuit with a resistance/potentiometer?

While running simulations for a circuit I measured the input and output impedance by simply adding a potentiometer, turn it up until the voltage peak to peak signal going out reached half and then ...
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### Why does moving this ammeter change the polarity of the applied voltage?

Note: I'm not an electrical engineer, I'm a materials engineer. So maybe this question has an obvious answer, but I couldn't find one with a Google search. I also have no idea if I tagged this ...
752 views

### Darlington array: How to output desired voltage at uln2803a driver colectors?

Someone suggested this driver array to get the current I need: datasheet I also need a 12V signal and about a current of 100mA in order to control a relay coil. My 12V signal would come from a logic ...
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### Why isn't this active rectifier circuit working?

I built the following active rectifier schematic on a breadboard, and inputted a 15 KHz 1V peak to peak sine wave from my signal generator. The output looked like a sine wave and I have no idea why. ...
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### Is MOSFET active device?

The V-I characteristics of MOSFET lies in the first and third quadrant. Therefore it should be passive device acc to me. But I have read that it is an active device. Can somebody tell what is wrong ...
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### Simplest latching circuit with press-ON hold-OFF button that can cut power when Raspberry Pi halts

So I'm making a battery-powered Raspberry Pi project, and it would be ideal if it could cut off power to the Raspberry Pi after the Raspberry Pi shuts down. It would also be ideal if the power for ...
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### Why are active loads used for transistor amplifiers?

I get it that voltage drop across active loads are less compared to passive loads and at the same time they offer high small signal impedance thereby increasing gain. I cannot understand why DC ...
105 views

### Is there a standard component that can "save" a certain current or voltage and what is it's name?

What I am thinking about is something like this analog equivalent of a flipflop: ...
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1 vote
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### How does an active device work as an oscillator when its output is fed back to the input?

In the book The Art of Electronics by Paul Horowitz and Winfield Hill, it is mentioned that "Device with power gain are distinguishable by their ability to make oscillators, by feeding some output ...
1 vote
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### How can a USB cable extender boost the signal without an external power source?

I've been searching online for a USB Cable extender for a rather long distance (let's say 10 meters). I'm familiar with the notion that the longer the cable, the weaker the signal might get, more ...
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### Z-parameters measurement in active circuits

What difficulty faced in measuring Z parameters in active circuits, how is it taken care of?,what is limitation at high frequency? I heard that we use inductor instead of open ckt and capacitor ...
1k views

### Detecting Specific PWM Signal Without Programming (Only Electronics Components)

I want to detect a specific PWM signal by electronic circuit components i.e. transistors, opamps, capacitors. update: I want to build simple ID system. I want to detect specific PWM signal for example ...
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### Why can't passive components transform energy from one form to another [closed]

In parts of electrical components active components can control the flow of current in a circuit but passive components cannot. What is the factor that gives active components the ability to control ...
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### Other active component principles of operation

Besides valves and transistors... On another question, someone talked about magnetic amplifiers, but they are slow. Are there any other kind of "would-be" transistors out there ? A transistor that ...
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### Advantages of depletion mode FET devices over enhancement MOSFETs

I've grown the impression that JFETs and depletion mode MOSFETs are not used very much nowadays, especially in new designs. I know that they need different bias networks, especially as discrete ...
312 views

### OP AMP as active negative resistors

Was reading about OP AMP and saw a article on "Active Negative Resistor" on wikipedia @ http://en.wikipedia.org/wiki/Negative_resistance. Question to the gurus: How practical is this? Can I build a ...
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### What to expect when i place a diode in magnetic field

I am designing a PCB that senses basic NTC values and converts it into digital format. The problem is the entire PCB is above a magnet(about 70mT at the board) that is moving. Hence i want to know ...
3k views

### How can I tell if a given MOSFET can be fully driven by 5V TTL high signal? (what should I look for on the datasheet?)

How can I tell (by reading the datasheet) if a specific MOSFET can be turned fully on (with the minimum drop) with simply 5V on the gate? (assuming 5V or 12V potential between the drain and source). ...
413 views

### Can electronic components work without power?

Can electronic components work without power,with the help of temperature? according to my knowledge,I don't think so,until heat will generate some energy and that will drive component. I have to make ...
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### Which is actually an active component? [duplicate]

"An active device or component is something which can provide an infinite energy or non-zero power for an infinite interval" I learned this definition for an active device in a book, which is valid ...
49k views

### What is the transfer function for a first order active high-pass filter

What is the transfer function for the below circuit? simulate this circuit – Schematic created using CircuitLab Since the op-amp has unity gain, the transfer function should be the same as a ...
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### Differential amplifier with active load Sedra Smith

I'm studing differential amplifiers on Sedra Smith book, and I have come across the following circuit. My question is: how can NMOS transistor $Q_2$ have a current $g_{m2}\cdot v_{id}/2$ if the ...
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### Power switch between two sources using mosfets

A new problem I have is to create an automatic switch between two sources, only one of the sources should be active at a time. There is a "backup" source (5V battery), as well as another source. Once ...
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### Why is Vbe a constant 0.7 for a transistor in the active region?

I'm going to take an example of a simple common emitter amplifier. Forget about biasing and things for now, but focus on the crux of this circuit. As how I understand it, a voltage between the base ...
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