Frequency conversion and computation with P-N junction devices

The usual assumptions of PN junction theory have been applied to frequency conversion. The matrix describing superheterodyne operation can be expressed in terms of the small-signal diffusion admittances and a matrix depending on the local-oscillator voltage. The analysis also gives the large-signal admittances of a PN junction. A sufficiently small bonded contact and the emitter junction of a high-frequency transistor are examples of structures that minimize minority-carrier storage and give minimum conversion loss in demodulation (converting a high frequency to a low frequency). Such structures are also useful for performing logical operations in computers. The empirically observed need for small points in point-contact diodes for microwave detection is explained. When the geometry favors storage of minority carriers near the junction, amplification is possible in modulation (converting a low frequency to a high frequency). Structures of this sort can be used as pulse amplifiers.