Active zener diode substitute circuit

Abstract

A circuit which performs regulator or limiter functions at current and voltage levels below the operating ranges of conventional zener diodes. The output of an op amp is connected through a diode to a main input terminal which may be connected between a power source and one end of a load resistor. A first current limiting resistor connects the main input terminal to the inverting input of the op amp. A second current limiting resistor connects the non-inverting input of the op amp to the wiper terminal of a potentiometer which permits adjustment of a simulated zener voltage V.sub.z. A pair of supply voltage terminals of the op amp are connected to voltages V.sub.cc and V.sub.ee, respectively. A pair of fixed terminals of the potentiometer are also connected to voltages V.sub.cc and V.sub.ee, respectively. The simulated zener voltage V.sub.z may be positive or negative, and may be adjusted to any value within limits determined by voltages V.sub.cc and V.sub.ee, the op amp saturation voltages, the current sinking capability of the op amp, and the voltage drop across the diode.

Dependencies are inferred from the claim text.