Electrical Engineering

Questions tagged [saturation]

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27 views

How to tell if a switching element is operating linearly?

For example, a p-mosfet in a buck or buck boost topology converter. Is it working optimally or inefficiently?
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2answers
6k views

Saturation regions for BJTs and MOSFETs

After reading this post (3rd answer): (https://electronics.stackexchange.com/a/129423/54580) I almost got it why the saturation regions of BJTs and MOSFETs are in different regions of their diagrams....
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1answer
129 views

Why does it take several seconds of time for the photodiodes to come out of saturation?

I am currently studying about photodiodes and came across this fact that photodiodes take quite a bit of time to come out of the saturation. What really happens during this time (after it is saturated ...
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1answer
262 views

Amplifier circuit - NMOS mode of operation? Gain?

Ok I have the following circuit, with values of variables: \$\displaystyle R_{1} = 1 M\Omega, R_{2}=10k\Omega,~~ k_{n}C_{ox}\frac{W}{L}=1mA/V^2\$ , and \$V_{T}=1V\$. 1) When \$v_{IN}=0\$, calculate ...
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1answer
1k views

LM3915 to drive more LEDs / basic questions about PNP transistors in saturation

As a few others here, I'm trying to drive a few (10) LEDs from each output of a LM3915 vu-meter chip. I've read different posts, and it seems the universal recommendation is this great answer. I have,...
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0answers
82 views

Can an inductor lose its characteristics permanently after short saturation?

I was testing a SMPS (boost) where I had an overcurrent due to overload for a few seconds. The inductor saturation current is 2A. Although I could not measure the current, I am quite sure that the ...
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1answer
1k views

Forced beta too small

Let's take an example in which the recommended beta for a transistor's(NPN) saturation is 10.If you use a forced beta smaller than 10,will the transistor still be saturated succesfully?Can hFE be ...
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0answers
240 views

one-sided saturation with op-amp and RC high pass filter

I am working with a photodetecting circuit built as follow: When I drive an LED ON and OFF, I get the following waveforms: Blue indicates that the LED is turned on when a voltage is high and turned ...
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0answers
536 views

Passive harmonic filter: Why Immensely Hot and Humming

I encountered a passive harmonic filter, PHF with highly non linear loads, i.e. variable frequency drive, VFD (most of the time running 50Hz) serving an induction motor. I believe that it is a ...
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0answers
424 views

Op-amp: Floating input (Multisim)

I found this circuit from Encyclopedia of Electronic Circuits Volumes 1 by RUDOLF F. GRAF I used Multisim to simulate. When switches S1 and S2 are open (U1A@3 and U1B@6 are floating) and I measured ...
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860 views

Unexpected saturation with the rail to rail instrumental amplifier AD623

I'm trying to use the rail-to-rail instrumental amplifier AD623. Here the datasheet. simulate this circuit – Schematic created using CircuitLab First experiment: AD623 set as a voltage ...
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3answers
259 views

Understanding transistor circuits

I have been working my way through The Art of Electronics by Horowitz and Hill and I've just started the chapter on Transistors. I am having some difficulty in understanding this transistor circuit: ...
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2answers
2k views

What is the difference between “Collector-Emitter” and “Base-Emitter” Saturation Voltage?

As you can see on the datasheet below for the 2n2222a NPN transistor, the "Collector-Emitter Saturation Voltage" and "Base-Emitter Saturation Voltage" are defined respectively as 0.3 to 1.0 and 1.2 to ...
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2answers
3k views

A confusion about the formula for transistor Vbe Ic characterisitcs

Below is NPN BJT transistor Vbe Ic characteristics and the formula: Many texts approximate this equation as: Ic = Is*e^(Vbe/Ut) and following this they say when Vbe=0, Ic becomes equal to Is. ...
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3answers
85 views

Transistor Analysis

Here is a problem I saw as an example of transistor analysis: (hFE is 50) simulate this circuit – Schematic created using CircuitLab The process is simple, the guy assumed that the transistor ...
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1answer
169 views

Photodiode amplification works with LM258N but doesn't with LF356N

The circuit is as follows I'm powering the op-amp from a 9V battery. It gives me constant 3.6V at the output and it doesn't change with changing the illumination of the diode. I tried replacing the ...
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2answers
559 views

What causes “positive feedback” in audio amplifier

I am currently using an audio amplifier to make a presentation. However, sometimes mid presentation the audio amplifier will go into a "positive feedback" mode where the sound coming out of the ...
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3answers
234 views

Trouble driving NPN into saturation [duplicate]

I can't saturate my NPN transistor! Here is my circuit: simulate this circuit – Schematic created using CircuitLab The Vce is around 1.7 V, which is way above the saturation Vce of 0.3, ...
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1k views

BJT: Equation of Vce for Saturation Region

In Sedra and Smith: Microelectronics Circuits (6E), it is mentioned, on page 185: Recalling that the CBJ is much larger than the EBJ, the forward-voltage drop \$v_{BC}\$ will be smaller than \$v_{...
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3answers
492 views

Microphone saturation avoiding desired signal from being detected

I'm trying to detect a known signal under heavy interference. I'm working with 2 smartphones and an interfering speaker. I'm sending a signal from one smartphone speaker to the other smartphone ...
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2answers
819 views

Transistor used as switch not working when connecting a water solenoid valve

As a summer project I am trying to create an automatic irrigation system. To do so, I created a circuit with a single transistor which will move from saturation to off and thus behave as a switch. ...
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3answers
65 views

Why does a rise in ambient temperature cause a base-voltage-biased grounded emitter stage to saturate?

This is actually exercise 2.9 in Horrowitz and Hill 2nd Ed. which is posed as: Verify that an \$8 ^\circ C\$ rise in ambient temperature will cause a base-voltage-biased grounded emitter stage to ...
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3answers
169 views

Why is one transistor in active and the other in triode?

Vtn = 0.4 V, W = 1um, L1=0.25um, L2=0.5um. For a question I got the circuit above, and the solution said that M1 is in triode and M2 is active. Also, V1 is unknown so I can't figure out how they ...
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1answer
2k views

Output resistance of a BJT in saturation

It seems by the characteristic curve of a BJT, that it behaves as a resistance in saturation region. Is this conclusion true? and if so how can I calculate this resistance (seen from collector) from ...
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1answer
447 views

Can an opamp be neither in linear region nor saturated?

I'm trying to build a voltage controlled DC current source. For this, I built this circuit: A little bit of context. The voltage supply is 5V. Current range must be from 0mA to 30mA or so. Load will ...
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3answers
339 views

Transistor saturation

I am trying to saturate a transistor , a BC547 A , but I am having a hard time figuring out something.What hFE should I use to compute the base and collector current to make it turn on fully? Here is ...
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1answer
54 views

How can I estimate the minimum beta for this driver to work in hard saturation?

Imagine I build the below LED driver circuit where I know all the component parameters such as 2V LED forward drop and resistors and Vcc and Vbb as in the following diagram: And if I only dont know ...
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1answer
179 views

How to Calculate Saturation Current of a Transformer?

Is this Method applicable to calculate? My confusion is mainly regarding with Load current. My knowledge is, that load current is nothing to do with saturation of transformer.
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1answer
74 views

How can a magnetic circuit with an airgap have a higher e.m.f in the secondary coil than the same circuit without the air gap?

I have a magnetic circuit with the same configuration as in the image, the primary coil has 203 turns and the secondary has 406 turns, how do I get a higher eletromotive force when there is an air gap ...
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1answer
3k views

Resistance of a MOSFET in saturation mode

I have been studying MOSFETs and have a question regarding saturation mode. To my understanding, the drain current is constant in saturation mode. Does this mean that the drain-source resistance ...
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1answer
49 views

Calculating minimum resistance such that Ic is less than or equal to the maximum Ic in BJT

This is what I have been given for the question. I'm confused on how to answer this question. I thought this was calculated just by using ohm's law where R = 5V(supply V) / .3A(max Ic) = 18. However ...
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2answers
522 views

Common base circuit with zero supply voltage

Consider a bipolar junction transistor (either PNP or NPN). Which output would produce this circuit for various input (\$= V_{\mathrm{BE}}\$) voltages? It is common base, but without a voltage supply ...
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2answers
96 views

saturation point of electrical iron

In my work with electrical iron, I have done a lot of research to try to understand how to determine the quality of it. Is there a simple way to test for the saturation point? Some of the methods I ...
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2answers
576 views

calculate resistor value for transistor base

Below is a circuit where S1 is the output of a 555 IC timer (S1 switch for simplicity). I need to invert the output which I have done so in another project using the circuit below. Starting with ...
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2answers
439 views

Would output signal affect input signal when the opamp is saturating?

I have learned that opamp would be saturating when the output signal is too large. My question is would the saturating output affect input signal, for example, change the amplitude of the input ...
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1answer
70 views

Magnetic material demagnetization through Curie temperature

It is known that some materials lose their permanent magnetic properties when they are heated above certain temperature known as Curie temperature or Curie point. As those materials are cooled down to ...
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1answer
55 views

BJT saturation question

For the following question, how do we find \$I_B\$ and \$I_C\$? Would it be $$I_C = \frac{V_{in}-V_{BE}}{80k}$$ and $$I_B = \frac{12-0.12}{5k}$$
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1answer
196 views

Differential amplifier circuit, problem with saturation

I have a homework problem regarding differential amplifier. We have a differential amplifier with symmetric supply (i.e. \$V_{CC}=-V_{EE}\$). Emitters are connected to a perfect current source \...
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1answer
549 views

Problem with output swing in LM358

simulate this circuit – Schematic created using CircuitLab I am working on a battery charger with indicator. I am using a LM358 to compare the voltage of my battery with a reference voltage of ...
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4answers
2k views

Negative voltage for Vce - BJT NPN

I was wondering what happens when VCE voltage becomes negative? suppose I am forwarding both junctions (no resistors). I know that saturation happens when VCE is between 0.1V- 0.3V but what happens ...
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2answers
555 views

Current gain characteristics versus Collector Emitter voltage. Where is the transistor saturated? Can a transistor be saturated with a VCE of -10V?

I'm fairly new to transistor usage and determining stages of operation for a BJT. However, from what I've learned, in order for a BJT to be saturated, both junctions need to be forward biased, and ...
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1answer
267 views

DC Shunt Generation Ascending/Descending Terminal voltage Saturation Curve help?

In a DC Shunt Generator we increased Field Current from 0 to 2.0 and calculated the Terminal Voltage, we then decreased field current from 2.0 to 0 and collected our field current again. When plotting ...
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1answer
283 views

Setting optimum base current for saturation and power dissipation of a BJT

Regarding the following circuit example, I want to find the optimum current for saturation of Q1. By saturation I mean the safe one. For simplicity I didn't bias the transistor and I'm assuming beta ...
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1answer
2k views

Active region in BJT in a Common emitter configuration

In BJT for working in active region for a common emitter configuration emitter and base should be in forward bias and base and collector should be in reverse bias. But in case of voltage we say that ...
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1answer
970 views

Saturation current in Ebers-Moll equations for BJT: what is it and how to measure it?

In Ebers-Moll Equations for common emitter BJT the inverse saturation current \$I_s\$ appears as a parameter. What is the saturation current \$I_s\$ exactly and how should I measure in a common ...
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1answer
649 views

PNP with zener diodes circuit

simulate this circuit – Schematic created using CircuitLab I am really struggling to understand how this circuit works theoretically. What will be the currents through the resistors? My ...
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2answers
2k views

How does a photodiode behave in saturation?

In my design, a photo diode is connected in reverse bias with 12V. The LDO (low-dropout) voltage regulator which is used for biasing can deliver a maximum current of 500mA My configuration: simulate ...
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1answer
1k views

Optocoupler 4N25 saturated CTR

I'm studying optocouplers in general, and in special the 4N25. I'm applying the optocoupler in a zero crossing circuit, like this one: I know the CTR is minimum of 20%, but checking the datasheet ...
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2answers
99 views

Long term effects of operating in Saturation mode of transformer

What are the long term effects of operating a transformer in Saturation mode? Let's say my transformer can deliver 1VA of power while operating in saturation mode and i consume around 0.6-0.7 VA. ...
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2answers
6k views

Reverse saturation current of BJT?

This might be a basic question...but I'm having a hard time understanding reverse saturation current in collector-base junction in the active region(Is), Could anyone explain about it? Its temperature ...

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