Stable transistor wide-band D-C amplifiers

Stable d-c amplification is required in many engineering applications. In the past, vacuum-tube circuits have been developed which meet most low drift requirements by utilizing differential amplification, chopper, and chopper stabilization techniques. Transistors offer many inherent advantages such as small size, long life, no filament power, low power dissipation and good reliability, but they in turn present new problems in design and techniques. Since the major source of drift in tube d-c amplifiers is filament power variations, the transistor might seem to have inherent advantages concerning drift. However, the variations of transistor parameters with temperature presents as formidable a problem as vacuum-tube filaments. Stable d-c amplifiers using transistors can be designed and constructed by modifying the basic techniques used in vacuum-tube circuits.