Abstract: The described invention relates to a regulator circuit.A transistor Q1 receives at an input terminal 1 an input voltage having D.C. and A.C. components and provides a regulated D.C. output voltage at an output terminal 4. The transistor Q1 lies in the negative feedback path of an operational amplifier 6 between an output 9 and an input 5 of that amplifier. The amplifier 6 also has a reference voltage input 8. A second operational amplifier 19 also receives the reference voltage at one input 20 and at its other input 18 receives a D.C. potential representative of the D.C. input component and has an output terminal 21 coupled to the output terminal 4 in such a manner as to regulate the value of the D.C. input component by control of current drawn through the transistor Q1. A third operational amplifier 32 also receives the reference voltage at one input 33 and at a second input 31 receives the A.C. component of the input voltage and passes the A.C.

Abstract: The invention relates to a signal processing arrangement which in a preferred form is part of a telephone speech circuit.The circuit arrangement includes an operational amplifier for processing signals coupled to an input terminal via a capacitor. In order to control output current provided by the arrangement a current is coupled to the input terminal of the amplifier which is fed with the signals to be amplified and an equal and opposite current is fed to the opposite side of the capacitor so that the effects of any unwanted A.C. components in the control current may be reduced.The use of the circuit allows a single capacitor to perform multiple functions thereby reducing the number of capacitors and the number of terminal pins of an integrated circuit package incorporating the circuit.The invention is particularly suitable for use in a telephone speech circuit.