Questions tagged [saturation]

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45
votes
9answers
90k 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 ...
31
votes
2answers
21k views

What is saturation in an inductor

I have heard a lot of the time that "the core is not large enough to handle the current, and will reach saturation". What is saturation and why is it a bad thing to reach saturation?
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 <...
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?
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'...
10
votes
6answers
3k views

Why do we want gap in the core material while designing inductor?

In some cases it is necessary that core of inductor should have a gap, unlike with transformer core. I understand the reason with the voltage transformer core; there is nothing to worry about core ...
8
votes
5answers
4k views

How to prevent op amp from saturating?

How can an op amp be prevented from going into saturation if the feedback is intermittently disconnected? For example, in this circuit (simplified case of a real-life problem), the op amp acts as a ...
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 ...
7
votes
2answers
958 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 ...
6
votes
1answer
363 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 ...
6
votes
2answers
260 views

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 ...
6
votes
2answers
619 views

Transistor in saturation mode?

I was wondering why do we so often want out transistor to work in saturation mode? Ie. For a MOS Current Steering Circuit we want our transistors to operate in the saturation region....
5
votes
2answers
261 views

Powering an LED with transistor in saturation mode

I currently try to design my first transistor circuit to switch an LED on and off. So I came up with this circuit diagram: I have to use the following components: PN2222A NPN BJT IR LED TSAL 6200 ...
4
votes
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 ...
4
votes
1answer
2k views

Diy inductor saturation current

I have a boost converter that will convert 12V and 11A to around 20V and 6A. Since I didn't find any inductors (in my local stores) capable of such currents and frequencies and the correct inductance ...
4
votes
3answers
155 views

What precisely is \$R_{ds(on)}\$?

I keep getting conflicting answers on this and it's absolutely killing me. Some say \$R_{ds(on)}\$ is the contact resistance in the FET (for instance, make many FETs of varying channel lengths, turn ...
4
votes
1answer
2k views

BJT differential amplifier output saturation

I'm making a long-tailed pair amplifier using a current mirror, the circuit has the following layout: I simulated it on PSpice and it worked, you can see the bias here: I tested it in the real ...
4
votes
3answers
171 views

Control System - Changing damping on-the-fly?

I'm trying to implement a PID algorithm on a microcontroller that controls an actuator with a hard physical limit. In MATLAB, there's no consequence to large overshoots/hitting saturation at high ...
3
votes
1answer
1k views

Vce saturation voltage confusion

I finally finished my first transistor circuit and looks as follows: For the LED to light up properly, I assumed a forward current of 70mA and a voltage drop of 1.3V. The datasheet of the PN2222A ...
3
votes
3answers
971 views

How to determine the saturation level when an opamp schmitt trigger starts worknig?

The Opamp inverting schmitt trigger is constructed as shown. The output signal is So I ask why is the output at the start of operation saturated to positive? Also, if the input voltage is moved ...
3
votes
2answers
545 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 ...
3
votes
3answers
77k views

What is reverse saturation current?

The official page of Wikipedia mentions that reverse saturation current is a part of minority current caused by the drift of charges. I am really confused about this. In class, we have been taught the ...
3
votes
1answer
314 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,...
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
1answer
100 views

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 ...
3
votes
4answers
2k views

NPN Circuit simulation doesn't agree with book

I'm trying to understand an exercise reported in Microelectronic Circuit Design by R. C. Jaeger & T. N. Blalock (4th ed, p.237). $$\beta_F = 50, \beta_R = 1$$. I don't agree with the discussion ...
3
votes
3answers
10k views

Determine saturation base current from NPN transistor datasheet (or what resistor do I need to ensure saturation?)

The Fairchild 2N3904 has a long data sheet so let's use that for this exercise. I'm interested in using an NPN in common emitter configuration --- it's for switching. It's my understanding that an ...
3
votes
1answer
175 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 ...
3
votes
1answer
4k views

Reverse saturation current in a BJT: active and reverse active modes

In (Sedra; Smith. Microelectronic Circuits), as well as in several other sources, the value of the reverse saturation current (\$I_S\$) is considered the same for the active mode and for the reverse ...
3
votes
1answer
214 views

DC Voltage Source - circuit problem

I'm currently trying to build a DC voltage source from an AC source to a school project. The circuit worked fine when it had no voltage regulator, as it was just a transformer + full-wave rectifier + ...
3
votes
1answer
60 views

Is there any way to use the saturation harmonics to determine the rated voltage of a induction motor?

When the motor is running at no-load, the core eventually saturates as the AC supply voltage is increased. Therefore, harmonics will be present in the AC supply current waveform . I suspect that 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 ...
2
votes
2answers
167 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 ...
2
votes
3answers
3k views

Push pull core saturation

I want to build a circuit similar to this one: I read that using push pull without per-pulse current limit or series with trafo cap can cause core to saturate because two pulses aren't perfectly ...
2
votes
2answers
558 views

Core saturation detector-differentiator

I am building some project that requires me to measure the saturation corrent of some homemade inductors winded on scavaged ferrite cores, so I decided to try and create a circuit that will aid me in ...
2
votes
2answers
5k views

Alternative to emitter-follower for simple BJT voltage regulator

I want to make a voltage regulator from one or two BJTs and a zener diode. However, I would like to be able to make full use of supply voltages when they are lower than the voltage that the regulator ...
2
votes
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 ...
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 ...
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
303 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 ...
2
votes
2answers
303 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
3answers
377 views

BJT Saturation with small load/ H-bridge

I am trying to analyze the operation of a BJT H-bridge configuration. I have searched through these forums and Google and can't seem to find an answer to my question. It is my understanding that it ...
2
votes
1answer
86 views

Verify that an increase in 8º C will saturate a common emitter

In the Art of Electronics there is an assertion that if a bias is established with 0.5 the supply voltage, the transistor will saturate if the temperate goes up 8ºC. The schematic is the basic one for ...
2
votes
1answer
282 views

coupled inductor in series

I'm planning on using a dual inductor in series mode to increase the inductance. I realize that the total inductance will be L1+L2+2M where M is the mutual inductance (when the polarity is connected ...
2
votes
1answer
268 views

Cannot find “reverse saturation current” of base-emitter junction in the data-sheet

Regarding the reverse saturation current \$I_{ES}\$ aka \$ I_{EO}\$ of an NPN transistor, according to Ebers–Moll Model: \$I_E = I_{ES} (e^{V_{BE}/V_T} -1) -\alpha_RI_{CS}(e^{V_{BC}/V_T}-1)\$ ...
2
votes
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 ...
2
votes
1answer
943 views

How is reverse saturation current of a BJT measured empirically?

I'm not asking the definition, but wondering how do the manufacturers measure this parameter's quantity in a lab for instance? For example for Ic Vce characteristics they keep Ib constant and they ...
2
votes
1answer
411 views

Confusion with MC34063 Vsat

I'm currently designing an e-ink panel driver. My choice is MC34063 for generating required voltages and I want to use two of these for step-up and inverting converters. However I'm somewhat confused ...
2
votes
1answer
107 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 ...
2
votes
2answers
928 views

How to conclude region of operation for a series combination of MOSFET

I understand that M1 is on and for M2 to be on the intermediate voltage(drain on M1 and source of M2) should be less than 1.5V. Also if M2 is ON then M2 is in saturation since Vds>(Vgs-Vt) for M2. Now ...