Quick Answer: How Do You Know If A BJT Is In Saturation?

What is saturation in BJT?

Saturation, as the name might imply, is where the base current has increased well beyond the point that the emitter-base junction is forward biased.

In fact, the base current has increased beyond the point where it can cause the collector current flow to increase..

What is the working of transistor?

A transistor is a miniature electronic component that can do two different jobs. It can work either as an amplifier or a switch: When it works as an amplifier, it takes in a tiny electric current at one end (an input current) and produces a much bigger electric current (an output current) at the other.

What happens when transistor is in saturation?

Saturation is the on mode of a transistor. A transistor in saturation mode acts like a short circuit between collector and emitter. In saturation mode both of the “diodes” in the transistor are forward biased. That means VBE must be greater than 0, and so must VBC.

How do you know if a transistor is saturated?

Monitor the collector-emitter voltage of your circuit with a DMM. If the reading is below 0.3V, the transistor is at saturation. Transistors are having saturation voltage range from 0.7V and below but for a circuit designed for hard saturation, the VCE will be lower.

What is the most frequently encountered transistor configuration?

The most commonly used circuit configuration is the common emitter – this is used for many amplifier stages providing voltage gain. The emitter follower or common collector is also widely used.

Why is emitter always forward biased?

Why emitter is always forward biased? Emitter is always forward biased w.r.t base so as to supply majority charge carriers to the base.

What is the PNP transistor?

The PNP Transistor is the exact opposite to the NPN Transistor device we looked at in the previous tutorial. … Then, PNP transistors use a small base current and a negative base voltage to control a much larger emitter-collector current.

Which parameters helps in finding whether the BJT is in saturation or not?

With the change in the external parameters like temperature, or with the replacement of the transistor the β may change. And with that change, the transistor may come out of saturation. So, to ensure the operation of BJT in the saturation region in all the conditions, the β in the saturation should be very low.

Why is VBE 0.7 V?

For an unbiased transistor, considering only the BE junction which is a pn junction diode, 0.7V is the potential barrier. In an npn transistor base is positive(p) and emitter is negative(n). … But in a pnp transistor the base is negative(n) and emitter is positive(p) so the vbe=-0.7V.

How do you calculate IC saturation?

Therefore Ic= a*Ie and Ic= B*Ib. Therefore Ic(saturation)<=aIe and Ic(saturation)<=BIb. And the corresponding saturation voltages are, Vbe(sat)= 0.8 volts, Vce(sat)= 0.2 volts, Vcb(sat)= -0.6 volts.

How do you calculate VCE saturation?

Vce(sat) is usually something like 0.2V, and it’s usually safe to use 0V as a first approximation. If we assume Vce(sat) of 0V, we get an Ic = 10V/500 ohms = 0.02A. Now we calculate how much base current we need to put the transistor in saturation with an Ic of 0.02mA. Ib(min) = 0.02A / HFE = 0.0002A.

How is IC Calculated?

How to Calculate the Collector Current, Ic, of a TransistorUsing Known Values.Example. If Ib=35μa and β=100, then Ic calculates out to be:Using Known Values.Example. If Ie=4ma and β=150, then the value of Ic is computed to be:Using Known Values. If base current, Ib, and emitter current, Ie, are known, then Ic can be calculated by the formula:Example.

What is ΒDC equal to?

βdc is the amplification factor by which the base current gets amplified by. So the total output current, IC will be IC=βdc x IB.

How does a BJT work?

Bipolar Transistors are current regulating devices that control the amount of current flowing through them from the Emitter to the Collector terminals in proportion to the amount of biasing voltage applied to their base terminal, thus acting like a current-controlled switch.

What is IC saturation?

Yes – there are two different meanings of the term “saturation” – dependent on the transistor type: BJT or FET. … BJT (with collector resistor): Increasing Vbe (or Ib) leads to rising collector current Ic, which causes a continuous decrease of the collector-emitter voltage Vce – until a lower limit is reached at app.

How do you calculate BJT mode?

Here I am giving the simplest and the easiest way to know the operating mode of BJT i.e. in which mode it is .Firstly you can easily say by looking at the dc biasing of emitter-base junction whether the base-emitter junction is forward bias or reverse bias . … Secondly, go for base current (Ib).More items…

What is reverse saturation current in BJT?

reverse saturation current is a current flow due to minority carrier from a neutral region to enlarging depletion region, this minority carriers are formed at junction due to thermally produced electrons and holes.

Is VBE always 0.7 V?

VBE is the voltage that falls between the base and emitter of a bipolar junction transistor. VBE is approximately 0.7V for a silicon transistor. For a germanium transistor (which is more rare), VBE is approximately 0.3V. Again, this formula, can be used for either silicon or germanium transistors.

Why VCE SAT is 0.2 V?

Because the charge carriers injected from the base effectively eliminate the depletion zone between the collector and emitter. The collector current doesn’t have to overcome the P-N junction potential because the base current has neutralized it.

What is the hFE of a transistor?

hFE of a transistor is the current gain or amplification factor of a transistor. hFE (which is also referred to as β) is the factor by which the base current is amplified to produce the amplified current of the transistor. … The datasheets will normally specify whether the hFE value is for DC or AC current gain.