transistorz

• BJT (Bipolar Junction Transistor) : A semiconductor device with three regions - emitter, base, and collector - that can amplify or switch electronic signals by controlling the flow of current between these regions
• Collector-feedback bias provides good stability using negative feedback from collector to base.
• Emitter bias provides good Q-point stability, but requires both positive and negative supply voltages.
• Base bias has poor stability because its Q-point varies widely with βDC.
• Emitter : The region in a BJT from which majority charge carriers (electrons or holes) are injected into the base region
• Base : The region in a BJT where the majority charge carriers injected from the emitter cross into the collector region
• Collector : The region in a BJT that collects the majority charge carriers that cross from the base region
• Gain : The ratio of output signal strength to input signal strength, indicating how much an electrical signal is amplified
• Beta (bDC) : The DC current gain of a transistor, representing the ratio of collector current to base current
• Saturation : The state of a BJT where the collector current reaches a maximum and becomes independent of the base current
• Linear : Characterized by a straight-line relationship of the transistor currents, typically referring to the active region of transistor operation
• Cutoff : The state in which a BJT is biased to prevent current flow between the collector and emitter, acting as an open switch
• Amplification : The process of increasing the strength or power of an electrical signal, often achieved using amplifiers like BJTs
• Phototransistor : A type of transistor where base current is generated when light strikes the photosensitive semiconductor base region, used in light-detection applications
• The relationship between the collector current and the light-generated base current is quantified by a parameter known as the current gain (β_DC).
• Common package types for general-purpose/small-signal transistors include plastic or metal cases, with certain types containing multiple transistors.
• The transistor behaves like an open switch between the collector and emitter in cutoff.
• RF transistors are designed for radio frequency and microwave applications, and they have specific package types tailored for high-frequency operation.
• In saturation, both pn junctions of the transistor are forward-biased, allowing the maximum collector current to flow.
• Phototransistors are commonly used in applications where light energy needs to be converted to an electrical signal, such as in optical sensors, light meters, and communication systems.
• Power transistors are used to handle large currents and/or voltages, commonly found in packages with mounting studs or heat sinks.
• Incident light on the collector-base pn junction generates a base current (I_l) that is directly proportional to the light intensity, resulting in an increase in collector current (I_C).
• Phototransistors are designed to offer a large area for incident light to maximize the generation of base current.
• The transistor behaves like a closed switch between the collector and emitter in saturation.
• Troubleshooting involves identifying circuit malfunctions and isolating failures to single components if necessary.
• Bipolar junction transistors (BJTs) are available in various package types for different applications, including general-purpose/small-signal devices, power devices, and RF (radio frequency/microwave) devices.
• The ability to operate as a switch makes transistors suitable for digital logic circuits, pulse generation, and power control applications.
• A phototransistor is similar to a regular BJT but with the base current produced and controlled by light instead of a voltage source.
• In cutoff, both pn junctions of the transistor are reverse-biased, resulting in essentially no collector current.
• The amplification factor of a BJT is typically represented by the parameter hFE or beta (β), which is the ratio of IC to IB.
• The three currents in a BJT are the base current (IB), emitter current (IE), and collector current (IC).
• The dc current gain of a transistor is the ratio of IC (collector current) to IB (base current) and is designated as bDC.
• bDC is usually referred to as hFE on transistor datasheets.
• Voltage amplifiers utilizing BJTs are commonly used in audio amplifiers, radio frequency circuits, and various signal processing applications.
• Values typically range from less than 20 to several hundred.
• The invention of the transistor by a team of scientists from Bell Laboratories in 1947 led to the Nobel prize in 1956 for William Shockley, Walter Brattain, and John Bardeen.
• To operate as an amplifier, the base-emitter junction of a BJT must be forward-biased, and the base-collector junction must be reverse-biased, a configuration known as forward-reverse bias.
• The base current (IB) in a transistor is significantly smaller than the collector current (IC) and emitter current (IE).
• Bipolar junction transistors (BJTs) can be used as voltage amplifiers to boost or amplify electrical signals.
• A transistor can be operated as an electronic switch in two states: cutoff and saturation.