How does a transistor switch on and off?
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.
What is transistor current?
This current consists of two constituents – Hole current (IhE) and Electron current (IeE). IeE is due to passage of electrons from base to emitter and IhE is due to passage of holes from emitter to base. Normally, the emitter is heavily doped compared to base in industrial transistor.
How is a transistor used in a pulse circuit?
Pulse Circuits – Transistor as a Switch. A transistor is used as an electronic switch by driving it either in saturation or in cut off. The region between these two is the linear region. A transistor works as a linear amplifier in this region. The Saturation and Cut off states are important consideration in this regard.
When does a transistor work as a switch?
The output will be zero. Actually, this is the ideal condition. Practically, some leakage current flows. Hence we can understand that a transistor works as a switch when driven into saturation and cut off regions by applying positive and negative voltages to the base. The following figure gives a better explanation.
What happens when a transistor is in off mode?
Assume that a transistor has an input voltage of 0V. This means that the base current is ‘0’ and when the emitter junction is grounded, then the emitter and base junction will not be in forwarding bias condition. So, the transistor is in OFF mode and the voltage value at the collector edge is 5V. Vc= Vcc – (IcRc)
How is a transistor arranged as a switc H?
If the circuit uses the BJT transistor as a switc h, then the biasing of the transistor, either NPN or PNP is arranged to operate the transistor at both sides of the I-V characteristics curves shown below. A transistor can be operated in three modes, active region, saturation region, and cut-off region.