A SIMPLE NEGATIVE IMPEDANCE CIRCUIT WITH NO INTERNAL BIAS SUPPLIES AND GOOD LINEARITY.

This paper presents a very simple and stable negative impedance circuit and contains an analysis, the fundamental characteristics and some applications of the circuit. The circuit is composed of two transistors and requires no circuit adjustment nor internal bias supplies. The characteristics of the circuit are controlled by the choice of resistors and are essentially independent of transistor parameters if the transistors have typically large betas. The circuit can also be regarded as a negative impedance converter. Its linearity is good over a wide operating range, in spite of its simplicity, being better than 1 over 50 of the negative region in one experimental example. The V-I characteristics of the circuit are essentially constant from dc to the order of the betacutoff frequency of the transistors. A set of simple design equations are given as well as more precise equations which may be used for further developments. A design example and its experimental results are shown to verify the usefulness of the theory and versatility of the circuit. Three fundamental applications of the circuit designed above are described briefly. The first example is a negative resistance amplifier producing 8.5 db of voltage gain. At a power output of 0.3 mw, the output distortion is 40 db below the signal output. The gain is constant from dc to 100 kc. The gain can be increased to over 40 db without significant instability. Author