Questions tagged [saturation]

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533 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
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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2answers
612 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
263 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
543 views

Avoiding opamp saturation - working with apd

i have avalanche photo diode with which i am trying to digitalize the current from TIA through a comparator, the diode biased using a HVDCDC the source is being a 20ns laser with a PRF of 3Khz the ...
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1answer
278 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
167 views

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 ...
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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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1answer
174 views

Does a saturated inductor radiate more?

Background: I am using a shielded inductor in a switching power supply, and am investigating an EMI issue. My hypothesis is that since the inductor is saturated, the magnetic field is no longer ...
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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
683 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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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 ...
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1answer
519 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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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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2answers
1k 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
311 views

How a switching PSU inductor overcomes the problem of saturation current?

If you open a switching step down converter like the one used in your desktop computer, you will only find that a relatively small torroidal transformer ultimately provide the power to the user. Sure,...
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2answers
221 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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1answer
686 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
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
566 views

Collector current decreases with the increase of base current in saturation mode of bjt

I'm new to BJT and i'm trying to understand the characteristics of bjt in different modes of it. In my book they explained that in saturation mode of bjt the collector current decreases even if i ...
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3answers
166 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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2answers
301 views

Negative value for saturation mode voltage of MOSFET

I want confirmation of whether a MOSFET is in saturation or not. I have calculated the condition using the formula \$V_{GS}-V_{tn}\$, and my answer is a negative value. Does it matter if the value is ...
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1answer
360 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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3answers
486 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
238 views

Opamp output saturates at 1.7V even though rail voltage is 5V

simulate this circuit – Schematic created using CircuitLab I am working on following circuit on a 4 layer PCB. The sensor gives output from 0.5V to 4.5V and has frequency response of 19 Hz ...
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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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1answer
357 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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1answer
925 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
618 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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4answers
247 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 ...
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1answer
100 views

Channel shape of NMOS in saturation

According to the Sedra/Smith Microelectronic Circuits textbook, 6/7 eds., increasing \$v_{DS}\$ beyond \$v_{OV}\$ has no effect on the channel shape and charge. Why is that? It seems as if (...
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2answers
302 views

A switching boost converter biasing a tube preamp - saturation issue

I am designing a 9V-battery powered tube preamp (for electric guitar), based on a Russian rod tube (1j24b). The latter is a pentode, and works with about 45V on its screen grid and at least 30V on its ...
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0answers
83 views

BJT Differential Amplifier deliberately saturated?

Happy New Year! I've recently completed a metal detector project (see my recent questions) and I've been going back over some of the parts I didn't fully understand first time around. This question ...
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1answer
78 views

Horowitz lab 4.4

I have a problem doing lab 4.4 from Horowitz's student manual for the Art of Electronics. Here's the circuit and here's what I get from LTspice simulation, which corresponds to hardware circuit ...
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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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2answers
7k views

A question about Vce of an NPN BJT in saturation region

Below is an NPN transistor symbol and the voltages at its terminals are Vb, Vc and Ve with respect to the ground: I read that: during the saturation the Vce = (Vc-Ve) settles to around 0.2V and the ...
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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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4answers
1k views

Why Op-Amp Saturation voltage drop with increasing frequency?

i was Implementation of square and triangular wave generator using op-amps LF353. I observed that when I choose different values of Resistor and Capacitor for different frequencies, with increasing ...
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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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3answers
3k views

Output Drift of an operational Integrator

R = 1k and C = 0.1 uF In practice, the output of and operational integrator will (drift) until it saturates at a value close to one of the supply voltages, even when the input voltage (Vin = 0). Why ...
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2answers
711 views

Correlation between saturation of high current (power) transformer core and load

In an experiment I need high (\$>600A_{max}\$ or \$1200A_{pp}\$) AC currents in a range from 400Hz to 4kHz. The load is simply a short circuit. For this purpose i use a class D audio amplifier and ...
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2answers
808 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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2answers
515 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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3answers
2k views

Terminology for BJT “regions of operation”

How regions (modes) of operation are defined and correctly named? The most controversial thing is the so named “saturated region/mode”. It is defined differently, sometimes radically different, in ...
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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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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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0answers
229 views

How does the source voltage change with and without channel modulation?

The description here seems big, but it's only a two minute read. I'm stranded, desperately need help. The variable resistance R in the figure is set to 10K ohms. The first question was to find the ...
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4answers
3k views

What happens after opamp saturates

here below is a TIA stage intended to do I-V conversion, as the maximum supply voltage being 5V for a given feedback resistance of 1K the opamp would saturate for a input current from photo diode of ...
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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. ...