Switching transistors are usually driven into saturation, which has an adverse effect on the switching speed. This effect is eliminated, or nearly so, by the use of Schottly diodes at the inputs. It is equally possible to add a diode to a transistor (across its base-collector junction) as shown in the diagram to increase its switching speed.
When the transistor is driven into conduction. Its base current will soon be limited because the diode has a lower transfer potential than the base-collector, junction so part of the current will flow through the diode. When the transistor is switched off, it will, therefore, require less time to reach the non-conducting state. The effect is seen clearly in the photograph. Signal I is the input signal at a frequency of 166 kHz. Signal 2 is the Inverted collector signal with the diode added. It is evident that owing to the diode, the collector returns to the high-level state much more rapidly.
A transistor is a type of semiconductor device that can be used to both conduct and insulate electric current or voltage. A transistor basically acts as a switch and an amplifier. In simple words, we can say that a transistor is a miniature device that is used to control or regulate the flow of electronic signals. Transistors are broadly divided into three types: bipolar transistors (bipolar junction transistors: BJTs), field-effect transistors (FETs), and insulated-gate bipolar transistors (IGBTs).
A transistor can act as a switch or gate for electronic signals, opening and closing an electronic gate many times per second. It ensures the circuit is on if the current is flowing and switched off if it isn’t. Transistors are used in complex switching circuits that comprise all modern telecommunications systems.
Bipolar transistors are a type of transistor composed of PN junctions, which are also called bipolar junction transistors (BJTs). Whereas a field-effect transistor is a unipolar device, a bipolar transistor is so named because its operation involves two kinds of charge carriers, holes and electrons.
