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In which mode BJT can be used as switch and amplifier?
If the transistor is biased into the linear region, it will operate as an amplifier or other linear circuit, if biased alternately in the saturation and cut-off regions, then it is being used as a switch, allowing current to flow or not to flow in other parts of the circuit.
Is amplifier a switch?
We also know that the transistor when used in the cutoff or saturation state, acts as a switch and then operated in the active region is used as an amplifier. In this piece of article, we will learn how a transistor is used as a switch and as an amplifier, in detail.
Which BJT is used as amplifier?
The circuit for determination of BJT I-V curve is depicted on the figure below. The most important dynamic characteristics of a BJT are it’s switching characteristics. In standard operation the BJT transistor works as an amplifier.
How does a BJT switch work in a switching circuit?
In a switching circuit, the goal is not to provide proportional changes in output current; rather, we simply want to drive the transistor into full conduction. Thus, a BJT switch transitions between cutoff mode and saturation mode. We don’t limit the input voltage or the input current in an attempt to keep the transistor in forward active mode.
How is the BJT differential pair a differential amplifier?
The differential pair is a differential amplifier—we express its performance in terms of differential and common-mode gains. Consider the BJT differential pair: 2 1 Also, we know that: Therefore, the emitter currents can be written in terms of the base voltages as: Of course, we know that Ii i= EE12+ , thus:
How to use BJT as a voltage amplification?
BJT Voltage Amplification. 1 Vb can be supposed as the ac input voltage for transistor. Here Vb =Vs- IbRB. 2 Vc can be taken as the ac output voltage of transistor. 3 As the ratio between the output to input is known as voltage gain. 4 So the ratio between Vc to Vb is ac voltage gain and denoted as Av.
How is a BJT used as an example?
Using a BJT as a Switch: An Example. Remember that the controlled current through a transistor must go between collector and emitter. Since it is the current through the lamp that we want to control, we must position the collector and emitter of our transistor where the two contacts of the switch were.