Patent ID: 6433636
Filing Date: 2002-08-13
Classification: H03F

Abstract:
An operational amplifier comprising:a differential amplifier including a first input transistor connected to an inverting input and a second input transistor connected to a non-inverting input, said differential amplifier being responsive to the input signal to the inverting input to establish a current flow through the first input transistor to provide a first signal and responsive to the input signal to the non-inverting input to establish a current flow through the second input transistor to provide a second signal; an output circuit including a first output transistor which is disposed in a current line extending from a positive voltage side of a dc power supply to an output terminal of the operational amplifier and which connects at a first terminal with the positive voltage side of the dc power supply and at a second terminal with the output terminal and a second output transistor which is disposed in a current line extending from a negative voltage side of the dc power supply to the output terminal and which connects at a first terminal with the output terminal and at a second terminal with the negative voltage side of the dc power supply; a control circuit supplied with a power from the dc power supply to control said output circuit, said control circuit working to produce a first drive signal to develop a drive voltage across the second terminal and a control terminal of said first output transistor in response to the first signal inputted from said differential amplifier and to produce a second drive signal to develop a drive voltage across the second terminal and a control terminal of said second output transistor in response to the second signal inputted from said differential amplifier so as to output a signal from the output terminal as a function of the potential difference between the input signals to the inverting input and the non-inverting input, said control circuit including a first control circuit designed to be responsive to the first signal outputted from said differential amplifier to control the first drive signal so as to decrease a current flowing through the first output transistor as a potential of the input signal to the inverting input rises and a second control circuit designed to be responsive to the second signal outputted from said differential amplifier to control the second drive signal so as to decrease a current flowing through the second output transistor as a potential of the input signal to the non-inverting input rises; and phase-compensating capacitors disposed between the output terminal of the operational amplifier and a portion of the first control circuit leading to the control terminal of the first output transistor and between the output terminal of the operational amplifier and a portion of the second control circuit leading to the control terminal of the second output transistor.