Comparison with vacuum tubes

Before transistors were developed, vacuum (electron) tubes (or in the UK "thermionic valves" or just "valves") were the main active components in electronic equipment.

Advantages[edit]

The key advantages that have allowed transistors to replace vacuum tubes in most applications are

• no cathode heater (which produces the characteristic orange glow of tubes), reducing power consumption, eliminating delay as tube heaters warm up, and immune from cathode poisoning and depletion;
• very small size and weight, reducing equipment size;
• large numbers of extremely small transistors can be manufactured as a single integrated circuit;
• low operating voltages compatible with batteries of only a few cells;
• circuits with greater energy efficiency are usually possible. For low-power applications (e.g., voltage amplification) in particular, energy consumption can be very much less than for tubes;
• inherent reliability and very long life; tubes always degrade and fail over time. Some transistorized devices have been in service for more than 50 years^{[citation needed]} ;
• complementary devices available, providing design flexibility including complementary-symmetry circuits, not possible with vacuum tubes;
• very low sensitivity to mechanical shock and vibration, providing physical ruggedness and virtually eliminating shock-induced spurious signals (e.g., microphonics in audio applications);
• not susceptible to breakage of a glass envelope, leakage, outgassing, and other physical damage.

Limitations

Transistors have the following limitations:

• silicon transistors can age and fail;
• high-power, high-frequency operation, such as that used in over-the-air television broadcasting, is better achieved in vacuum tubes due to improved electron mobility in a vacuum;
• solid-state devices are susceptible to damage from very brief electrical and thermal events, including electrostatic discharge in handling; vacuum tubes are electrically much more rugged;
• sensitivity to radiation and cosmic rays (special radiation-hardened chips are used for spacecraft devices);
• vacuum tubes in audio applications create significant lower-harmonic distortion, the so-called tube sound, which some people prefer