Questions tagged [saturation]

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Some questions about BJT in saturation region

In below circuit I sweep Vb from zero to 5V Vcc. And I obtain the following plots for the currents: I have a bit problem with understanding two things in saturation region: 1-) Why/how does the Ic ...
2
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1answer
236 views

Questions regarding BJT saturation for a circuit

I have the following circuit which converts weak sine signal to pulses: I have tried it on breadboard and it seems it works fine. In my application freq. is between 1Hz to 30Hz or max 100Hz. And the ...
2
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1answer
537 views

Why does the reverse saturation current not vary with the reverse voltage?

I can understand that in the depletion region of a diode more covalent bonds are broken(more electrons goes to conduction band) with more temperature hence we say that the reverse saturation current ...
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4answers
249 views

Control voltage required to turn on the LED through an NPN

simulate this circuit – Schematic created using CircuitLab For this circuit, I am trying to figure out the value of \$V_1\$ DC which will turn on the LED, D1. Since the forward voltage drop of ...
2
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1answer
197 views

Dual Op Amp should be saturating but it is instead tracking the negative pin input

I was attempting to implement figure Figure 34 on the AD734 datasheet in multisim (the national instruments SPICE simulator) Based off what I know of op amps, the output of U2b should be saturated to ...
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3answers
2k views

Bypassing Transistors with a Switch, problems?

While working on a design last night, I had a question pop up. Is there any risk in bypassing a transistor, with a jumper/switch? Or shorting the Collector and Emitter pins with a wire? Is there a ...
2
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1answer
73 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 ...
2
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1answer
73 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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2answers
1k views

Op-amp saturation problem

My design: Two cascade connected inverting amplifiers. My problem: The output of second amplifier is saturated from -0.6 to -0.7V. The supply of OPAMPs is dual (+5-5V). What is the problem? How ...
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3answers
10k views

Why does the opamp output voltage saturate?

simulate this circuit – Schematic created using CircuitLab Vout = Vin (1 + R2/R1) According to this positive feedback topology - made an error here, it's Vout = Vin(-R2/R1) (edit) Now I ...
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2answers
639 views

Why are the transistors in logic circuits used in saturation region for ON state?

This is a beginner question. I know how the logic gates with BJTs work basically to provide ON and OFF switching action. OFF state occurs when the transistor is blocked in cut-off region, and ON state ...
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1answer
364 views

NPN Switch when ON operating in Forward Active or Saturation Region?

When an NPN transistor is used as a switch as shown below, is it operating in the Forward Active Region or the Saturation region when it is turned ON? I believe its working in the Forward Active ...
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2answers
6k views

How to find a saturation current for BJT from datasheet?

Saturation Current is one of parameters in Ebers Moll Model, but I can't find it in datasheets. I explore SC1627 and BC856 datasheets. How to find it? As opposed to How do I saturate an NPN ...
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2answers
217 views

BJT in Saturation

Is it possible for the base current to exceed the collector current for a BJT in saturation mode? (If the base current was increased without the collector current increasing at all)
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3answers
986 views

How is this BJT in saturation?

I simulated this circuit using Qucs: With Vin = 5V, VB = 0.746V and VC = 0.024V which means ...
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2answers
1k views

Is inductor saturation current frequency dependent?

The wiki article explaining inductor core saturation talks about magnetic domains lining up with the external magnetic field to concentrate the magnetic flux. This sounds similar to electric ...
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3answers
740 views

How to measure the inverse saturation current of a diode?

I'm trying to measure the inverse saturation current of a diode, for using it in the schockley equation. I would like to know what is the best circuit for doing this. I already tried the following ...
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2answers
225 views

What causes a transistor to enter into the saturation mode?

I'm looking into the construction of logic gates, and am wondering what conditions are need across emitter-base-collector in terms of both voltage and current to enter the saturation mode. For ...
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3answers
3k views

How to solve BJT amplifier clipping a signal?

I'm trying to make an audio amplifier for an 8 ohm speaker. I'm new in electronics area and having a problem with it. I already had other issues before arriving where I am, like the need of a high ...
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3answers
887 views

Transistor saturates no matter the size of base resistor

Problem I have a circuit as depicted below, and after calculating the base resistor, I wanted to see when the base current would be too little to saturate the transistor. I kept increasing the ...
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1answer
48 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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2answers
1k views

Newbie question - sawtooth signal generation - capacitor discharge via bjt

I'm trying to realize a sawtooth wave generator. The circuit is composed by an op-amp integrator which creates the ramp. Then the integrator output is chained to a comparator with a fixed threshold, ...
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2answers
1k views

Op Amp saturating below supply voltage?

I would like to know why op-amps saturate below their supply voltage. For instance I have a circuit with an LM358-N amplifier IC that is powered at +5 [V] and connected to ground on the other rail. ...
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2answers
410 views

Why does a Schmitt trigger work in saturation region?

Given this circuit simulate this circuit – Schematic created using CircuitLab I am trying to prove that the opamp works in saturation region as instructed in the first answer to this question :...
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2answers
4k views

Common emitter characteristics in the saturation region

I'm trying hard to understand the different modes and regions of operation of BJTs. The behavior of transistor in saturation region is so confusing. I've searched in forums but couldn't get a ...
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2answers
812 views

Voltage Follower Saturation

I'm trying to use a 0.5V signal as a source. I've wired a TL072CN as follow: VCC+ to 11V VCC- to GND OUT2 to IN2- IN2+ to 0.5V The thing is when I measure the voltage on OUT2 I get 10V where I am ...
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2answers
36 views

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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2answers
41 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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3answers
67 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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2answers
259 views

Saturating magnetic field in an inductor without heating

I am building an RL series circuit with a toroidal inductor that I am winding on my own. The toroid is made of steel (low carbon, I believe, but not 100% sure) and has about 280 turns of 22 gauge wire....
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1answer
106 views

Opamp circuit problem

BJT Circuit Problem I have already posted a similar problem in the link above. I am facing the same issue in this circuit. What will be the state of the 2 BJT's Cutoff, Saturated or Active ? Please ...
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1answer
451 views

Inductor Inrush Current Rating

I am experimenting with the simple circuit shown below and was wondering how to ensure that the inductor used would handle the inrush current. My reasoned solution is the following: I solved for ...
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2answers
375 views

Saturation in differential pair

I'm reading Analysis and Design of Analog Integrated Circuits by Gray & Meyer. In the differential pairs' chapter, there is this circuit and it says: Assume the collector resistors are small ...
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3answers
1k views

Photodiode in photovoltaic mode, overcoming saturation

can anyone explain to me why moving to configuration (b) overcame the problems I was having with the photodiode saturating? Many thanks, John
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2answers
404 views

Why doesn't Class C modulator operate in saturation?

The following circuit is a class C (actually class B) amplifier used in AM modulator in my previous question. According to the textbooks, the transistor is driven into saturation in this class. A ...
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2answers
368 views

Linear operating range of an amplifier as a function of frequency

How does the linear operating range of an amplifier (the linear part of the function that describes Power Out vs. Power In), both in theory and in practice, vary with frequency? In other words, if I ...
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4answers
2k views

Confusion in interpreting NPN transistor's saturation region

Above screen-shot is from a SPICE simulation of an NPN BJT where it shows the output characteristics Vce versus Ic. Ib is kept constant at 5uA where Vce increased from 0V to 5V. I'm having difficulty ...
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1answer
238 views

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
127 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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2answers
233 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
159 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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1answer
266 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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1answer
39 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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1answer
701 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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1answer
365 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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2answers
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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2answers
109 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
3k 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
872 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
209 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 ...