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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MOS current mirror region of operation

The mosfet M1 is clearly in saturation as gate and drain terminals are shorted. Why we take M2 also in saturation? I know Vgs1 = Vgs2 and they are identical MOS but i cant justify why M2 should be in ...
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Transistor - Saturation and Active Regions

I am using this BC817-40 transistor as a switch. In the above image, we can see that inorder to operate my transistor in the saturation region, I need to make sure my Ic/Ib ratio is less than 40. ...
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Buffer op amp amplifier saturation

I have designed a buffer amplifier using an LM358 op-amp, with an input of a 1kHz sine wave and a power supply of +/-6V. whenever I increase the input sine amplitude above a certain threshold, I get a ...
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The meaning of constant current source in BJT

Taking a sample from TAOE Ch.2 Figure 2.9 for example. The book suggests that BJT constructs a constant current source for the LED and \$\beta\$ is subject to change from multiple parameters thus ...
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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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Current Mirror Circuit

Below is a sample current mirror circuit. I understand that If the transistor Q1 is connected in a diode connected BJT configuration and the Transistor Q1 and Q2 have identical transistor parameters, ...
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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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83 views

How to calculate Ic for a very simple NPN transistor circuit

I built a very simple circuit with an NPN (2N3904) transistor. Then, I swept Vce from 0 to 5V and plotted a Vce vs Ic graph (as shown in the picture). I heard Ic = Is*e^(Vbe/VT), where VT=0.025V, and ...
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58 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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46 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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39 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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66 views

Magnetic field saturation in ac circuit

We have an AC voltage source connected to an ideal inductor that has no resistance.The inductor is wound around a ferromagnetic material. The maximum value of the driving voltage source is big enough ...
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Using MOSFET to prevent Op Amp saturation

How N-channel Q1B MOSFET prevent Op-Amp U1B from saturation.Terminal 5 of U1B and Q1B are connected to output voltage of a DAC. At 4 of Q1B and Q2B is the same signal multiplexed to control LED.
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What happens when transistor operates in saturation region for constant current source

I am learning about the constant current sources and I found this video What I dont understand is that, when the forward voltage of the LED is increased from 1.7V to 3.3V, and our Emitter voltage is ...
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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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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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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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op amp saturation

I have this circuit which is acting with negative resistance. However when increasing the voltage well above saturation it produces a weird distortion on the output as seen below. can anyone explain.
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Inverting op amp design saturates at a fraction of power supply

I have built a simple inverting op amp. I am applying a 1 Vpp sinusoid at 10 Hz to a design with ~4.7x gain. The resistors I am using are 47kOhm and 10 kOhm. The op amp chip is the LT1222, and I am ...
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On interpreting this set of curves (Transistor in Saturation mode and decrease of \$h_{FE}\$)

The following figure was excerpted from Horowitz's The Art of Electronics, Appendix G: Transistor Saturation (page 1089 for the 2nd edition), It represents the current gain \$\beta\$ of an npn ...
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1answer
124 views

Rectified current transformer output is asymmetric

I'm using a current transformer (CS4200V-01L) to measure the current in a half-bridge. I'm facing an issue where the signal out of the current transformer is asymmetric, almost as if the current ...
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1answer
51 views

How can U_CE be smaller than U_BE in this circuit?

Recently I was wondering why UCE can be smaller than UBE. I've drawn a small diagram with the typical values of the BC547 NPN transistor. This amazes me all the more as UBE shares its PN-regions with ...
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393 views

What are these transistors doing and how are they working in this VU Meter?

I was thinking of making KITT's voice box from Knight Rider, which is essentially a VU meter. I did some researching and found an appropriate IC, LM3916, http://www.mouser.com/ds/2/405/lm3915-443929....
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583 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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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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Instrumentation Amplifier Saturation to Rails

I am working with a TI INA821 Instrumentation Amplifier to try to amplifier a 0-5mV (delta) analog signal off a strain gauge. To reiterate, every DC analog value between the delta of 5mV represents a ...
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53 views

Magnitude of \$I_{CBO}\$ in a typical transistor

I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current ...
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107 views

Saturation current on chip inductors

Inductors are really not my strong point, and I have been getting a bit confused on the rated current vs saturation current. I know the rated current is how much current the inductor can handle ...
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88 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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174 views

Do BJT (Darlington) transistors have a minimum collector current?

I am using a TIP122 Darlington transistor. From the graph provided in the datasheet, I can see that the saturation voltage decreases as the collector current decreases. Since the load I am driving ...
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170 views

Why isn't the saturation current of a photodiode the same as its short circuit current?

The formula I see everywhere is: $$ I_{sat} = \frac{V_{bias}}{R_L} $$ But this seems incomplete for the following reason: The larger the resistance is the smaller the saturation current, it stands ...
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102 views

What part of Ebers-Moll equation shows the decrease of the collector current in saturation region

By looking at the Ebers-Moll equation for a BJT transistor: Is this formula explicitly showing why Ic starting to decrease towards zero in saturation region. Which part of the equation shows that?
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295 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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135 views

MOSFET goes into saturation mode much later

I am using IRLML6346 NMOS in LTSpice. Its threshold voltage is Vt = 0.95V. I plotted the graph of Vds(voltage between drain and source) vs Ids(Current from drain to source) for different values of Vgs(...
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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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167 views

NMOS/PMOS Saturation

If I recall correctly, saturation occurs if \$V_{GS}>V_{TH}\$ and \$V_{DS}>V_{Dsat}\$ for NMOS. But is there an upper limit for the voltage? Like, when does a transistor not saturate after ...
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164 views

Double BJT circuit with one BJT off and one in saturation

In the circuit below, due to the base voltage, the circuit becomes a common-emitter setup. However, assuming a reasonable value for the base current the BJT should be in saturation. However the value ...
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85 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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Self-made Schottky transistor doesn't behave as I'd expect

For a project of mine I need to generate UART-like signals with higher voltage (up to 18V) and a baudrate of 115200 bps and later possibly 250000 bps. I tried a basic BJT level shifter which worked as ...
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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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228 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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170 views

OPAMP saturating when output is negative, simulation is OK

The schematics: It should convert 0-3.3V input from the DAC to -4.1 + 4.1V (roughly) The positive part works great, the negative output voltage saturates at -2.95V. Is it ok? The simulation looks ...
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182 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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654 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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369 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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Why collector current is small in value in saturation mode?

Why is the collector current smaller in value when a transistor is in saturation mode of operation? My guess is that although both the junctions are forward biased, the (forward) currents are '...
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224 views

JFET saturation current

Is it possible to analytically calculate Idss for JFET? I tried by setting voltage gate-source to zero, and then finding the drain current, but it doesn't seem to match with the given value?
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Why this operational amplifier is saturated?

my problem is that in this circuit: Where \$\pm V_{cc} =\pm 15V, R1=1k\Omega, R2= 10k\Omega\$, if I introduce a signal like: \$ v_i(t) = 2 \cos{(2\pi 1000 t)}\$, the output voltaje is this: Where ...
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Simulating Chua's circuit in LTspice with a saturating transformer-based nonlinear resistor

Chua's circuit is one of the simplest circuits known to exhibit chaotic behavior. It consists of resistors, capacitors, an inductor, and an active nonlinear resistor. One implementation of this ...
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205 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 ...