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Questions tagged [saturation]

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7
votes
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 ...
2
votes
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 ...
45
votes
9answers
89k views

How do I saturate an NPN transistor?

I understand that in "saturation mode", a BJT functions as a simple switch. I've used this before driving LEDs, but I'm not sure I understand clearly how I got the transistor into that state. Does a ...
13
votes
4answers
54k views

How do BJT transistors work in a saturated state?

This is what I know about NPN BJTs (Bipolar Junction Transistors): The Base-Emitter current is amplified HFE times at Collector-Emitter, so that Ice = Ibe * HFE <...
12
votes
2answers
5k views

Prevent high-side BJT saturation

I am building high-speed (10-20ns on BC847-class transistors) digital "buffer"/"inverter" out of BJTs. Scheme is attached. While I can prevent saturation of low-side BJT by adding Schottky diode, it'...
0
votes
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. ...
13
votes
2answers
17k views

Calculating the saturation current of an inductor?

How can I calculate saturation current of a Toroid inductor, with a core? What effect does the current have on the inductivity after crossing the saturation current?
0
votes
1answer
927 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 ...
1
vote
2answers
5k 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....
1
vote
1answer
105 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 ...
0
votes
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 ...
0
votes
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 ...
7
votes
2answers
951 views

Why does a C4467 transistor turn off slowly when collector-emitter current is low

I built the following circuit simulate this circuit – Schematic created using CircuitLab The clock has an amplitude of approx. 5 VDC. It's provided by a 555. I used two different values of R2 ...
1
vote
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 ...
2
votes
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 ...
1
vote
2answers
407 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 :...
0
votes
2answers
721 views

Unsaturated BJT

I'm struggling for an answer to part (c), I can do the first two questions. I know that \$i_C = \beta \times i_B\$, however, I don't know how to calculate the maximum current gain of the unsaturated ...
6
votes
1answer
362 views

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 ...
3
votes
3answers
9k views

BJT - absolute maximum base current?

Let's look at the datasheet for an MMBT3904, just for example. The absolute maximum section talks mostly about maximum voltage differences, and a single current limit - the collector current. I'm ...
3
votes
2answers
544 views

BJT Circuit Problem [closed]

I am facing problem in solving such mixed circuits with bjt, diode, opamp and Zener diode. In the above problem 1.zener can have 3 states (ON, OFF, Reverse ON) 2.diode can have 2 (ON, OFF) 3.BJT ...
2
votes
1answer
546 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 ...
2
votes
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 ...
2
votes
1answer
1k views

What does limit transferable power through a transformer?

Assume that there is a transformer as in the image above. The applied primary side voltage \$E_1\$ is always AC. We design the transformer so that the magnetizing flux \$\Phi_m\$ does not saturate the ...
1
vote
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 ...
1
vote
2answers
216 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)
1
vote
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. ...
1
vote
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 ...
1
vote
3answers
691 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 ...
0
votes
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 ...