Contents
Are transistors driven by current or voltage?
Basically, a bipolar transistor amplifies a small current entering the base to produce a large collector current. It is a current-driven device since the collector current is controlled via the base current. The current gain varies with the collector-emitter voltage (VCE).
Why transistor is a current operated device?
In a transistor, emitter current= base current+collector current. It means emitter current controls the collector current and base current. Therefore, the change in collector current is related with the base current and not to the base voltage change. That is why, the transistor is a current operating device.
Is a voltage-controlled device?
A voltage-controlled resistor (VCR) is a three-terminal active device with one input port and two output ports. The input-port voltage controls the value of the resistor between the output ports. VCRs are most often built with field-effect transistors (FETs). Two types of FETs are often used: the JFET and the MOSFET.
What do you need to know about transistors and relays?
However, most devices you’d want to control need more current than that to operate. You need a component in between your microcontroller and the device that can be controlled with this small voltage and amperage. Relays and transistors are most often used for this purpose. A relay is a switch that’s controlled by a small electric current.
How are transistors used to control high voltage?
Transistors are often used as electronic switches, to control loads which require high voltage and current from a lower voltage and current. The most common example you’ll see of this in a physical computing class is to use an output pin of a microcontroller to turn on a motor or other high current device.
Why are multiple transistors used in a bipolar transistor?
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.
What are the operating conditions of a transistor?
Here the operating conditions of the transistor are zero input base current ( IB ), zero output collector current ( IC ) and maximum collector voltage ( VCE ) which results in a large depletion layer and no current flowing through the device. Therefore the transistor is switched “Fully-OFF”.