A TRANSISTOR D-C NEGATIVE IMMITTANCE CONVERTER
JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB
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The ideal converter has a voltage transfer of minus one, a current transfer of unity, and acts like an ideal transformer with a negative input immittance. The circuits described are similar to those suggested by Linvill with one important difference. Due to the fact that there are two basic kinds of transistors, NPN and PNP, one may cascade transistors without resorting to coupling condensers. This fact is used with the result that a zero frequency converter is obtained consisting of two transistors and four resistors. Negative resistances may be obtained in a variety of ways. One specific configuration that converts a passive load to its negative is described using the small signal equivalent circuit to obtain various limiting conditions imposed upon the transistor and the frequencies of conversion. Equations are derived to permit the design of a specific converter. Due to the direct coupling the question of temperature sensitivity is discussed. One obvious use of a negative immittance is in oscillator circuits.
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