How does transistor work as a switch?

How does transistor work as a switch?

One of the most common uses for transistors in an electronic circuit is as simple switches. In short, a transistor conducts current across the collector-emitter path only when a voltage is applied to the base. When no base voltage is present, the switch is off. When base voltage is present, the switch is on.

What is the use of BD139 transistor?

BD139 is a Bipolar NPN transistor, it is mounted in the SOT-32 plastic package. It is designed for audio amplifier and driver utilizing complementary circuits. BD139 has a gain value of 40 to 160, which determine the amplification capacity of a transistor.

Which transistor is best for switching?

Best Transistors: BJTs

  • #1 NPN – 2N3904. You can find most often NPN Transistors in low-side switch circuits.
  • #2 PNP – 2N3906. For high-side switch circuits, you need a PNP style BJT.
  • #3 Power – TIP120.
  • #4 N-Channel (Logic Level) – FQP30N06L.

Can I use BD139 instead of BD140?

BD140 Alternatives The complementary NPN transistor to BD140 is BD139.

How use bc547 transistor as a switch?

TRANSISTOR AS A SWITCH It just bypasses the signal present of the collector while having active base condition. As soon as we press the button a signal (in form of voltage and current) will be received by the base of BJT which in turn allows electric current to pass from collector to emitter.

Why do we use transistor as a switch?

The transistor can be used as a switch if biased in the saturation and cut-off regions. This allows current to flow (or not) in other parts of a circuit. Because a transistor’s collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch.

How can a PNP transistor be used as a switch?

For a PNP transistor, the Emitter potential must be positive with respect to the Base. Then the transistor operates as a “single-pole single-throw” (SPST) solid state switch. With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows.

What is BC548 transistor?

The BC548 is a general-purpose NPN bipolar junction transistor commonly used in European and American electronic equipment. It is notably often the first type of bipolar transistor hobbyists encounter and is often featured in designs in hobby electronics magazines where a general-purpose transistor is required.

How can I use NPN transistor as a switch?

NPN Transistor as a Switch Based on the voltage applied at the base terminal of a transistor switching operation is performed. When a sufficient voltage (VIN > 0.7 V) is applied between the base and emitter, collector to emitter voltage is approximately equal to 0. Therefore, the transistor acts as a short circuit.

How a BJT can be used as a switch?

What is D882 transistor?

The D882 is a general-purpose transistor that belongs to the NPN transistor family. It comes with collector current 5A and is mainly used for switching and amplification purpose. The amplification factor is 60-400. This factor indicates the amount of current this device can amplify.

Why is BC547 used?

BC547 is usually used for current amplifier, quick switching and pulse-width modulation (PWM). Therefore, if you need to control the speed of a motor or actuator in some of your projects, you can simply use this transistor to achieve it.

What is a transistor switch?

Transistor switches can be used to switch a low voltage DC device (e.g. LED’s) ON or OFF by using a transistor in its saturated or cut-off state When used as an AC signal amplifier, the transistors Base biasing voltage is applied in such a way that it always operates within its “active” region, that is the linear part of the output

Why do we use multiple switching transistors in bipolar transistors?

Sometimes the DC current gain of the bipolar transistor is too low to directly switch the load current or voltage, so multiple switching transistors are used. Here, one small input transistor is used to switch “ON” or “OFF” a much larger current handling output transistor.

Can a PNP transistor be used as a switch?

PNP Transistor Switch We can also use the PNP Transistors as a switch, the difference this time is that the load is connected to ground (0v) and the PNP transistor switches the power to it. To turn the PNP transistor operating as a switch “ON”, the Base terminal is connected to ground or zero volts (LOW) as shown.

How does a transistor turn on and off?

With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows. With a positive signal applied to the Base of the transistor it turns “ON” acting like a closed switch and maximum circuit current flows through the device.