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The basic structure of a transistor is two PN interfaces connected in reverse, and the SMT transistor data indicates that there can be two combinations: PNP and NPN. The three connected endpoints are sequentially referred to as emitters (E) and (collector, C), and the source of SMT transistor data names is related to their functions during transistor operation. It also displays the circuit symbols of NPN and PNP transistors, with the emitter specially marked and the arrow indicating an n-type semiconductor, consistent with the symbol of the diode. When no external bias is applied, both pn interfaces will form depletion zones, separating the neutral p-type and n-type regions.

The electrical characteristics of a transistor are related to the bias voltage of the two pn junctions, and the operating range is also classified according to the bias voltage method. Here, we first discuss the most commonly used so-called "forward active region". In this region, the pn junction between EB electrodes is maintained at a forward bias voltage, while the pn junction between BC electrodes is maintained at a reverse bias voltage. Transistors commonly used as amplifiers are biased in this way. A schematic diagram of a PNP transistor in this bias region. The empty region of the EB interface will narrow due to forward bias, resulting in a smaller potential barrier observed by the carrier. The holes from the emitter will be injected into the base, and the electrons from the base will also be injected into the emitter; The depletion region of the BC interface will become wider, and the potential barrier seen by the carrier will become larger, so it is not conductive itself. The distribution diagram of the potential energy of holes and electrons is drawn under two conditions: no applied bias voltage and bias voltage in the positive active region. What is the difference between a transistor and two pn diodes connected in reverse? The biggest difference between them is that the two junction surfaces of the transistor are quite close. Taking the pnp transistor with bias voltage in the forward active region as an example, the hole of the emitter is injected into the n-type neutral region of the base, immediately surrounded and shielded by most carrier electrons, and then diffuses towards the collector direction, while also being recombined by electrons. When the uncomplicated holes reach the depletion region of the BC junction, they are accelerated by the electric field in this region and swept into the collector. The holes are the majority carrier in the collector and quickly reach the Ohmic junction outside the connection through drift current, forming a collector current IC. The size of the IC has little to do with the magnitude of the reverse bias between BC. The external part of the base only needs to provide the electron flow IBrec that combines with the injected hole, and the electron flow InBE that is injected into the emitter by the base (this part is not required for the action of the transistor). InB E combines with the hole at the emitter, i.e. InB E=IErec. The main type of current in the forward active region of the PNP transistor can be clearly seen in Figure 3 (a). The hole current injected into the base by the emitter is controlled by the forward bias voltage between the EB junction, similar to the case of a diode, near the starting voltage.

The basic structure of a transistor is two PN interfaces connected in reverse, and the SMT transistor data indicates that there can be two combinations: PNP and NPN. The three connected endpoints are sequentially referred to as emitters (E) and (collector, C), and the source of SMT transistor data names is related to their functions during transistor operation. It also displays the circuit symbols of NPN and PNP transistors, with the emitter specially marked and the arrow indicating an n-type semiconductor, consistent with the symbol of the diode. When no external bias is applied, both pn interfaces will form depletion zones, separating the neutral p-type and n-type regions.

The electrical characteristics of a transistor are related to the bias voltage of the two pn junctions, and the operating range is also classified according to the bias voltage method. Here, we first discuss the most commonly used so-called "forward active region". In this region, the pn junction between EB electrodes is maintained at a forward bias voltage, while the pn junction between BC electrodes is maintained at a reverse bias voltage. Transistors commonly used as amplifiers are biased in this way. A schematic diagram of a PNP transistor in this bias region. The empty region of the EB interface will narrow due to forward bias, resulting in a smaller potential barrier observed by the carrier. The holes from the emitter will be injected into the base, and the electrons from the base will also be injected into the emitter; The depletion region of the BC interface will become wider, and the potential barrier seen by the carrier will become larger, so it is not conductive itself. The distribution diagram of the potential energy of holes and electrons is drawn under two conditions: no applied bias voltage and bias voltage in the positive active region. What is the difference between a transistor and two pn diodes connected in reverse? The biggest difference between them is that the two junction surfaces of the transistor are quite close. Taking the pnp transistor with bias voltage in the forward active region as an example, the hole of the emitter is injected into the n-type neutral region of the base, immediately surrounded and shielded by most carrier electrons, and then diffuses towards the collector direction, while also being recombined by electrons. When the uncomplicated holes reach the depletion region of the BC junction, they are accelerated by the electric field in this region and swept into the collector. The holes are the majority carrier in the collector and quickly reach the Ohmic junction outside the connection through drift current, forming a collector current IC. The size of the IC has little to do with the magnitude of the reverse bias between BC. The external part of the base only needs to provide the electron flow IBrec that combines with the injected hole, and the electron flow InBE that is injected into the emitter by the base (this part is not required for the function of the transistor). InB E combines with the hole at the emitter, i.e. InB E=IErec. The main type of current in the forward active region of the PNP transistor can be clearly seen in Figure 3 (a). The hole current injected into the base by the emitter is controlled by the forward bias voltage between the EB junction, similar to the case of a diode, near the starting voltage.