Frequency and/or phase characteristic control circuit having controlled current multiplying ratio

Claim 1

A frequency and/or phase characteristic control circuit comprising: (a) a current multiplier having a multiplying ratio and containing an input terminal to be supplied with an input voltage, a voltage/current converter supplied with said input voltage so as to produce a pair of current signals at the output thereof, a pair of diode junctions supplied with said pair of current signals, a differential amplifier having first and second transistors and a current source, said first and second transistors being supplied with the voltage across said pair of diode junctions to produce a multiplied output current, and an output terminal connected to the output of said differential amplifier so as to produce output voltage across a load resistor proportional to said multiplied output current; (b) an operational amplifier having an in-phase input terminal, an out-of-phase input terminal and an output terminal; (c) a capacitor connected between the output terminal of said current multiplier and the out-of-phase input terminal of said operational amplifier; (d) a first impedance connected between the input terminal of said current multiplier and the out-of-phase input terminal of said operational amplifier; and (e) a second impedance connected between the out-of-phase input terminal and the output terminal of said operational amplifier; wherein the frequency and/or phase of the output signal of said operational amplifier is controlled by varying the multiplying ratio of said current multiplier.