Patent ID: 7449871
Filing Date: 2008-11-11
Classification: G05F

Abstract:
1. A system for setting an electrical circuit parameter at a circuit output at a predetermined value, the system comprising: a first electrical component having a first electrical parameter associated therewith; sensing means arranged to generate a control signal indicative of a value of said first electrical parameter; a second electrical component having a second electrical parameter associated therewith, the value of which has a predetermined relation to the value of the first electrical parameter; adjustment means arranged to receive the control signal generated by the sensing means, and in response to the control signal being indicative that the electrical circuit parameter at the circuit output is not at the predetermined value and the control signal being generated independently of any deviation of the circuit output, to selectively connect or disconnect at least one further electrical component to or from an output path of the second electrical component thereby to provide said predetermined value at the circuit output; and an oscillator having an operating frequency dependent on (a) the value of the first resistive component, and (b) a capacitor element associated with the oscillator, the control signal generated by the sensing means being derived from the difference between the operating frequency of the oscillator and a reference frequency and is effective to set the capacitance of the capacitor element at such a value that the operating frequency of the oscillator is modified to be substantially the same as the reference frequency.