Gain controllable amplifier circuit

An amplifier circuit comprising:

• first voltage-current converter means for converting an input signal voltage into a corresponding first output current;
• second voltage-current converter means for converting a negative feedback signal voltage into a corresponding second output current, said second voltage-current converter having first and second input terminals to which a DC voltage of a predetermined level and the negative feedback signal voltage are applied, respectively;
• coupling means for coupling said first and second output currents of said first and second voltage-current converter means, and for generating an output voltage corresponding to the sum of said first and second output currents;
• voltage amplifier means for applying the output voltage of said coupling means;
• feedback means for supplying part of the output voltage of said voltage amplifier means as the negative feedback signal voltage only to the second inputs terminal of said second voltagecurrent converter means, the DC voltage level of the output voltage of said voltage amplifier means being determined in accordance with both the negative feedback signal voltage supplied from said feedback means and the DC voltage of the predetermined level;
• and
• control means for controlling the ratio of the mutual conductances of said first and second voltage-current converter means.