Transistor

The transistor is a solid state semiconductor device which can be used for amplification, switching, voltage stabilization, signal modulation and many other functions. It acts as a variable valve which, based on its input voltage, controls the current drawn by it from a connected voltage supply.

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:

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• Smaller size (despite continuing miniaturization of vacuum tubes)
• Highly automated manufacture
• Lower cost (in volume production)
• Lower possible operating voltages
• Operation without a warm-up period (most vacuum tubes need 10 to 60 seconds to "warm up")
• Lower power dissipation (no heater power, very low saturation voltage)
• Higher reliability and greater ruggedness to physical shocks (although vacuum tubes are more resistant to nuclear electromagnetic pulses (NEMP) and electrostatic discharge (ESD) )
• Much longer lifetime (vacuum tube cathodes are eventually exhausted)
• Complementary devices available (allowing circuits with complementary symmetry?complementary vacuum tubes 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)
• Non-microphonic (vibration can modulate vacuum tube characteristics)

" Nature abhors a vacuum tube " John R. Pierce, Bell Telephone Laboratories, circa 1948.

Related Topics:
John R. Pierce - Bell Telephone Laboratories

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