Transistor functions as a switch. Explain.

Explanation

The transistor in saturation and cut-off regions functions like an electronic switch that helps to turn ON or OFF a given circuit by a small control signal।

Presence of de source at the input (saturation region): When a high input voltage (V। = +5V) is applied, the base current `(I-B)` increases and in turn increases the collector current। The transistor will move into the saturation region (turned ON)। The increase in collector current `(I_C)` increases the voltage drop across R, thereby lowering the output voltage, close to zero। The transistor acts like a closed switch and is equivalent to ON condition।
Absence of de source at the input (cut-off region):
A low input voltage `(V_in = OV)`, decreases the base current `(1_B)` and in turn decreases the collector current `(1_C)`। The transistor will move into the cut-off region (turned OFF)। The decrease in collector current `(1_C)` decreases the drop across Rc, thereby increasing the output voltage, close to +5 V। The transistor acts as an open switch which is considered as the OFF condition। It is manifested that, a high input gives a low output and a low input gives a high output। In addition, we can say that the output voltage is opposite to the applied input voltage। Therefore, a transistor can be used as an inverter in computer logic circuitry