Tuning method and apparatus for circuits to conform to a predetermined frequency response

摘要

An integrated circuit (ICT) comprising a filter (50). The filter comprises an input (Vin+) for receiving an input signal and an output (56) for producing an output signal having a frequency cutoff point. The filter further comprises at least one resistor network (RN1) coupled between the input and the output. The resistor network comprises a first non-switched resistance (R1.1) and a first resistance series connection connected in parallel with the first non-switched resistance. The first resistance series connection comprises a switched resistance (R1.2) connected in series with a source/drain path of a switching transistor (TRR1.2), the switching transistor having a gate for receiving a control signal. The frequency cutoff point is adjustable in response to the control signal. Moreover, ICT includes an oscillator required to conform to a predetermined frequency of oscillation, the oscillator comprising a second network of switchable resistors that is similar to the network of switchable resistors of the circuit which defines the frequency of oscillation of the fabricated oscillator, variations in said fabrication process having a similar deleterious effect on conformance of said oscillator with said predetermined frequency of oscillation; means for applying control signals to said second network of switchable resistors to bring said frequency of oscillation of fabricated oscillator into conformance with said predetermined frequency of oscillation; and means for applying the same control signals to said network of switchable resistors (RN1).