industrial applications of transistors
HI DEAR,
In the early days of transistor circuit design, the bipolar junction transistor, or BJT, was the most commonly used transistor. Even after MOSFETs became available, the BJT remained the transistor of choice for digital and analog circuits because of their ease of manufacture and speed. However, the MOSFET has several desirable properties for digital circuits, and since major advancements in digital circuits have pushed MOSFET design to state-of-the-art. MOSFETs are now commonly used for both analog and digital functions.
BJT used as an electronic switch, in grounded-emitter configuration
Amplifier circuit, minimal common-emitter configuration
[edit] Switches
Transistors are commonly used as electronic switches, for both high power applications including switched-mode power supplies and low power applications such as logic gates.
[edit] Amplifiers
From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.
Transistors are commonly used in modern musical instrument amplifiers, where circuits up to a few hundred watts are common and relatively cheap. Transistors have largely replaced valves in instrument amplifiers. Some musical instrument amplifier manufacturers mix transistors and vacuum tubes in the same circuit, to utilize the inherent benefits of both devices.
[edit] Computers
The "first generation" of electronic computers used vacuum tubes, which generated large amounts of heat and were bulky, and unreliable. The development of the transistor was key to computer miniaturization and reliability. The "second generation" of computers, through the late 1950s and 1960s featured boards filled with individual transistors and magnetic memory cores. Subsequently, transistors, other components, and their necessary wiring were integrated into a single, mass-manufactured component: the integrated circuit. Transistors incorporated into integrated circuits have replaced most discrete transistors in modern digital computers.
[edit] Advantages of transistors over vacuum tubes
Before the development of transistors, vacuum tubes (or in the UK thermionic valves or just valves) were the main active components in electronic equipment. The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are:
Smaller size (despite continuing miniaturization of vacuum tubes)
Highly automated manufacture
Lower cost (in volume production)
Lower possible operating voltages (but vacuum tubes can operate at higher voltages)
No warm-up period (most vacuum tubes need 10 to 60 seconds to function correctly)
Lower power dissipation (no heater power, very low saturation voltage)
Higher reliability and greater physical ruggedness (although vacuum tubes are electrically more rugged. Also the vacuum tube is much more resistant to nuclear electromagnetic pulses (NEMP) and electrostatic discharge (ESD))
Much longer life (vacuum tube cathodes are eventually exhausted and the vacuum can become contaminated)
Complementary devices available (allowing circuits with complementary-symmetry: vacuum tubes with a polarity equivalent to PNP BJTs or P type FETs are not available)
Ability to control large currents (power transistors are available to control hundreds of amperes, vacuum tubes to control even one ampere are large and costly)
Much less microphonic (vibration can modulate vacuum tube characteristics, though this may contribute to the sound of guitar amplifiers)
" Nature abhors a vacuum tube " Myron Glass (see John R. Pierce), Bell Telephone Laboratories, circa 1948