A transistorized decade amplifier for low-level audio-frequency applications

The amplifier descrbied in this paper has an input resistance of approximately 400,000 ohms in the audio-frequency range. The output noise level is equivalent to 5 µv at the input terminals with a response that is down 3 db at 5 cycles and at 100 kc. The amplifier has been designed in a self-contained package, the size of a frozen orange juice can suitable for plugging into the standard banana plug terminals of a sensitive vacuum tube voltmeter. The design may be modified, with considerable reduction in volume, to incorporate the amplifier in a small package with a low signal source.