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How do you determine if a transistor is saturated?
A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation.
What happens when transistor is saturated?
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. Because the junction from base to emitter looks just like a diode, in reality, VBE must be greater than a threshold voltage to enter saturation.
What is iC saturation?
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 cutoff region?
Whenever we observe the terminals of a BJT and see that the emitter-base junction is not at least 0.6-0.7 volts, the transistor is in the cutoff region. In cutoff, the transistor appears as an open circuit between the collector and emitter terminals. In the circuit above, this implies Vout is equal to 10 volts.
What is saturation voltage of a transistor?
“Saturation” in a transistor switch circuit is achieved when the voltage across the collector/ emitter (VCE(sat)) is less than or equal to . 1 to . 3 volts – depending on the type of transistor. At that voltage point, the transistor appears to act like a simple SPST mechanical switch that has been closed (On).
When is the base resistor in hard saturation?
Your circuit might be TTL and feeding 5-V, or perhaps CMOS, feeding 3.3-V. In this example, to make the maths simple, let us say that the switching voltage is 10-V at the input. When the transistor is in hard saturation, the entire switching voltage (10-V), will be effectively across the base resistor.
What happens in the saturation region of a transistor?
Saturation Region Here the transistor will be biased so that the maximum amount of base current is applied, resulting in maximum collector current resulting in the minimum collector emitter voltage drop which results in the depletion layer being as small as possible and maximum current flowing through the transistor.
How to calculate base resistance of a transistor?
Therefore, with simple transposition of the above formula, the following formula provides the base resistance: Rb = (Vi – Vbe) / Ib. To guarantee that the transistor operates in the saturation region, we multiply the base current by a factor of three.
What is the DC current gain of a base resistor?
This resistor determines the amount of saturation current I b (sat) flowing into the base junction, and that controls the amount of saturation current I c (sat) flowing through the collector and emitter junctions. For hard saturation, engineers usually use a DC current gain h FE value of 10.