Patent ID: 7075367

Claim:
An amplifier circuit comprising: an input (In) and an output (Out) and an internal node ( 10 ); an input transistor (Q 1 ) with a first control electrode coupled to the input (In) and a first main current channel coupled to the internal node ( 10 ); an output transistor (Q 4 ) with a second control electrode coupled to the internal node ( 10 ) and a second main current channel coupled to the output (Out); an internal transistor (Q 2 ) with a third main current channel coupled to the internal node ( 10 ), characterized in that a main low-frequency current path from the first main channel (Q 1 ) to the second control electrode (Q 4 ) does not pass through the third main current channel (Q 2 ); the amplifier circuit comprising: a resistive element (R 1 ), the internal node ( 10 ) being coupled to a power supply connection via the third main current channel (Q 2 ) and the resistive element (R 1 ) in that order, wherein a resistance value of the resistive element (R 1 ) exceeds a critical value above which poles ( 34 b, c ) of a transfer function of the amplifier circuit develop a real frequency component in order to raise amplifier cut-off frequency and optimize broadband gain.