Abstract: This disclosure depicts a substantially constant capacitance circuit for use with an external circuit having a variable voltage signal across first and second terminals. The circuit produces a constant capacitance across the terminals as the voltage signal varies. The value of capacitance is adjustable. The capacitance circuit comprises a first variable voltage source having its positive terminal operatively connected to the first terminal and a second variable voltage source having its positive terminal operatively connected to the second terminal. First, second, third and fourth reverse biased diodes are provided. The first diode is connected across the first voltage source and the fourth diode is connected across the second voltage source. The second diode is connected from one side of the first voltage source to the opposed side of the second voltage source and the third diode is connected between the first and second voltage sources in an opposite configuration to the second diode.

Abstract: A series pass voltage regulator compares the output voltage with a reference voltage and adjusts the base bias of a PNP series pass transistor coupled between an unregulated voltage source and a load to maintain the output voltage at a predetermined constant value. A current sensing resistor senses the base current of the PNP series pass transistor and limits the base current to a predetermined value indicative of a maximum allowable load current.