Amplifier circuit having low parasitic pole effect and buffer circuit thereof

An amplifier circuit having low parasitic pole effect, comprising:

• a pre-amplifier, configured to generate a pre-amplified signal according to an input signal;
• an output transistor, configured to generate an output signal according to a driving signal applied to a control end of the output transistor;
• and
• a buffer circuit, configured to generate the driving signal according to the pre-amplified signal, wherein the buffer circuit comprises:
• a buffer input transistor, configured as a non-inverted follower, wherein a control end of the buffer input transistor is controlled by the pre-amplified signal to generate the driving signal at a non-inverted output end of the buffer input transistor and to generate an inverted control signal at an inverted output end of the buffer input transistor, and an input impedance of the control end of the buffer input transistor is less than an input impedance of the control end of the output transistor;
• a first low output impedance circuit coupled to an inverted output end of the buffer input transistor, wherein an output impedance of the first low output impedance circuit is less than an output impedance of the inverted output end of the buffer input transistor;
• a first amplifier transistor controlled by the inverted control signal to generate a first amplified signal at an inverted output end of the first amplifier transistor;
• and
• an amplifier stage circuit, configured to amplify the first amplified signal to generate a second amplified signal, wherein a magnification ratio exists between the second amplified signal and the inverted control signal, wherein the second amplified signal is coupled to the driving signal, so that an equivalent output impedance of the non-inverted output end of the buffer input transistor is less than or equal to a product of an intrinsic output impedance of the non-inverted output end of the buffer input transistor and a reciprocal of the magnification ratio.