Table of Contents
- 1 How does a BJT work as a switch?
- 2 When a transistor is used as a switch in what two states is it operated?
- 3 Between which region does BJT acts like a switch?
- 4 What does a BJT do?
- 5 How does electricity flow through an LED?
- 6 What happens if you short an LED?
- 7 Why does the led of a square junction transistor stay on?
- 8 Why led does not glow when transistor is cut off?
How does a BJT work as a switch?
Bipolar junction transistor (BJT) has three terminals and two junctions. The function of the transistor is to amplify the signal. The transistor acts as a switch in the cut-off mode and the saturation mode. The transistor is fully off in the cutoff region and fully on the saturation region.
When a transistor is used as a switch in what two states is it operated?
In an ideal switch, the transistor should be in only one of two states: off or on. The transistor is off when there’s no bias voltage or when the bias voltage is less than 0.7 V. The switch is on when the base is saturated so that collector current can flow without restriction.
What happens if you turn the LED around in the circuit?
LEDs, being diodes, will only allow current to flow in one direction. And when there’s no current-flow, there’s no light. Luckily, this also means that you can’t break an LED by plugging it in backwards. A reversed LED can keep an entire circuit from operating properly by blocking current flow.
Between which region does BJT acts like a switch?
Between which regions does BJT act like switch? Explanation: In cut off mode a BJT is an open switch and in saturation mode it is a closed switch.
What does a BJT do?
As with all transistors, the basic function of a BJT is typically to function as a switch or to amplify, filter, and rectify power. Bipolar transistors are current-controlled and operated devices, meaning that a much smaller base current causes a larger current to flow from emitter to collector.
In which state is the switch said to be on?
When the transistor is not conducting, it is said to be switched off and when it is Region C it is said to be switched on.
How does electricity flow through an LED?
LEDs, being diodes, will only allow current to flow in one direction. The positive side of the LED is called the “anode” and is marked by having a longer “lead,” or leg. The other, negative side of the LED is called the “cathode.” Current flows from the anode to the cathode and never the opposite direction.
What happens if you short an LED?
If one LED goes open circuit then the other LED in the same line will go out. If one LED goes short-circuit then the other LED will light up brighter, and will die sooner – if not almost immediately depending on voltages and tolerances etc.
When can a BJT be used as a switch?
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. This lab activity describes the BJT when operated as a switch.
Why does the led of a square junction transistor stay on?
Due to cutoff no current flows through collector the led will not glow. When the magnitude of the square signal is large transistor is a saturation region. This state makes led forward biased and current flows through led that glows it. Hence led remains on for one second and off for one second.
Why led does not glow when transistor is cut off?
Due to cutoff no current flows through collector the led will not glow. When the magnitude of the square signal is large transistor is a saturation region. This state makes led forward biased and current flows through led that glows it.
What is the base-emitter junction in a BJT circuit?
When the input equals – Vin , the base-emitter junction is reverse biased or off so no current flows in the collector. This is illustrated by the load line shown in the figure. When the BJT is in cutoff, the circuit (ideally) has the following values: