Questions tagged [saturation]
Saturation applies to two things in electronics; core saturation in a transformer or inductor, AND transistor saturation in a BJT or a MOSFET.
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NMOS saturation mode: why is there no channel?
I have a question about the saturation mode. The cross-section of an NMOS transistor in saturation mode is usually drawn like this:
But it seems to me that there can be no current from source to ...
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1answer
129 views
Saturating a BJT with an open load
Is there some drawback in having a BJT transistor saturating without a load?
The scenario is this: BJT is driving a relay, but there is a switch to have the relay always on or off leaving the BJT ...
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166 views
What happaned when the flyback transformer is in saturation?
I am trying to design a DC-DC flyback converter.
Input voltage is 110V and output voltage is 24V. I have used NCP1252A PWM controller.
Flyback transformer windings:
Primary -> 24 turns
Secondary -...
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1answer
50 views
Remedy for pulling the output to ground in saturation?
Following ubiquitous common emitter configuration receives 0-5V logic input at its base such that the transistor goes into saturation or cut off mode:
So the output taken at collector is either zero ...
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350 views
Where would Iceo flow through and would it cause thermal runaway?
I was reading this page about thermal run away.
And it mentions:
Due to increase in the temperature of collector junction, Ico will
increase, Vbe will decrease.
But for Ico to increase Ic and ...
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1answer
212 views
Saturation Cascade MOSFETS (Need Help from EE Experts)
this is a very straightforward question.
I'm running a Harmonic simulation on ADS where I need to design a cascode amplifier of two NMOS and one PMOS, that have a gain higher than Av > -100. The ...
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450 views
Do we have a voltage drop across this ideal current source?
Additional info includes Vss=0V, Vdd=3V.
Also assume saturation (since we have Vd=Vg) and λn=0.
We also know the reference current but not the Resistor.
I know Vgs and thus Vds but I am looking to ...
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43 views
Is possible to get Q2 saturated with the VI voltage?
I´m having trouble with this circuit. Is it possible to get Q2 --> saturation using the VI voltage?
When VI = 0; the VCE2 = 14.457 V.
By calculations I know that Q1 and Q2 cannot be on saturation at ...
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877 views
Current waveform distortion on transformer with a load resistor on secondary winding
Why does the current from a transformer with a load resistor quickly rise and fall (yellow wave-form)?
(Transformer without a load resistor (white, primary)).
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426 views
Collector voltage in saturation
I saw the following question online
I knew that while Vbe was less than 0.6v, there would be no current and the collector voltage would be Vcc. At 0.6V, I knew that the transistor would turn on, and ...
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2k views
Reverse saturation currents of a LED?
What are the typical values of reverse saturation current of a LED? In particular is it possible to have a reverse saturation current of \$10^{-17} A-10^{-18} A\$ for a (red) LED?
For a silicon diode ...
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130 views
output voltage of an operational amplifier
A student designs an electronic sensor to monitor whether the temperature in a refrigerator
is above or below a particular value. The circuit is shown below.
Question: An operational amplifier (op-...
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1answer
4k views
Analysis of Class C AM modulator
The following schematic is a class C AM modulator without use of any transformers I've just changed the parameters in spice to get a correct modulation. however I want to find the theoretical value ...
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1answer
1k views
decreasing base current on saturated npn transistor
I would like to know if decreasing the current at the base on a saturated transistor(as in the attached photo) will cause the transistor gain to increase and by that, to maintain the collector current....
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1answer
220 views
Using a COTS common mode choke on DC
Are commercially available common-mode chokes, such as one you'd pull out of a dead switching supply, suitable for DC service up to their rated current, or will they saturate/do other baleful things ...
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2answers
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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8k 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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1answer
132 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
269 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
32 views
Detecting AC current using saturated current transformer — variation in saturation ampere-turns of magnetic cores
In another question someone asked about using a transformer (in current transformer mode) to detect current through a power line. The purpose of circuit was not to measure the current, but was only ...
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1answer
38 views
Motor rewinding - saturation concerns
After reading a lot about 3 phase BLDC motors there's one concern that's nowhere to be found.
Let's say that we have a 1000 Kv motor and we want to rewind it to 10 Kv to get unrealistically high ...
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61 views
Understanding the VI output characteristic of NPN transistor in the saturation region
I have trouble in understanding the VI graph of the output current (collector current \$I_C\$) in the NPN transistor. More precisely the common base one (this is the first type of transistor I came ...
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32 views
Buffer Clipping Below Negative Supply Voltage
I'm trying to understand op-amp operation, starting with the buffer circuit. I have simulated the voltage follower using an LM324 in Multisim Live. I was trying to simulate output saturation by ...
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84 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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2answers
2k views
Why Does Op-Amp Output Voltage Always Saturate (in a Non-Inverting Amplifier Circuit)?
I am trying to amplify the voltage measured across a shunt resistor (Rs). I am using a non-inverting amplifier circuit (as shown in the figure). The expected voltage across the shunt is in the 0-50mV ...
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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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271 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
643 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
434 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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875 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
279 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
5k 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
109 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
269 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
676 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
270 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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3answers
711 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
1k 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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1answer
42 views
Does turning on inductive load (ex. AC motor) at peak input voltage reduce inrush current?
I was checking out the following project on hackster and at some point the author claims that
When the load is predominantly of inductive type, the turn-on is performed at the peak of the input ...
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3answers
189 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
482 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
384 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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2answers
192 views
MOSFET regions of operation
Let's say I have a MOSFET already operating in saturation such that
Vds > Vgs - Vth. Can I make it to operate in triode or linear region by simply varying the drain voltage such that now Vds < (...
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1answer
63 views
Can't get 2N3904 transistor to allow the collector current I want, when used as a switch
I have a 3.7 V 18650 battery and I want to control a 3 V, 130 mA LED (high power CREE LED).
I have calculated the series resistor for the LED (0.7 V/0.130 A) = 5 Ohms (ish)
But when I apply any ...
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1answer
41 views
BJT working in saturation mode
I have the following circuit.
The transistor is working in saturation mode. It means both p-n-junctions are forward-biased. Thus, there are two diffusion currents in transistor (electrons move from ...
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1answer
77 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
1k 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
91 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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2answers
873 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 ...
