Amplifier having improved capacitive drive capability

An amplifier having a low output impedance comprising:

• a differential amplifier first stage having first and second inputs and an output, wherein the first and second inputs are inverting and non-inverting first stage amplifier inputs, respectfully;
• a third stage having an input and a first output, said third stage being a unity voltage gain, non-inverting stage;
• a second amplifier stage intermediate the first and third stages and coupling the output of the first stage to the input of the third stage, with the third stage and the second stage being implemented such that there is a negative voltage gain greater than unity between the output of the first stage and the first output;
• and
• a dominant pole capacitor which functions to establish a dominant pole in the frequency response of the amplifier, the dominant pole capacitor having one terminal connected to the output of the first stage and a second terminal connected to the first output and with the first stage, the second stage, the third stage and the dominant pole capacitor being implemented in a common monolithic integrated circuit;
• a second output;
• an isolation resistor coupled between the first and second outputs;
• a second capacitor coupled between the first output and the first input;
• and
• a feedback resistor coupled between the second output and the first input;
• whereby the dominant pole capacitor provides a direct feedback path between the output of the first stage and the first output so as to reduce the open loop impedance of the amplifier stage at the first output;
• and
• whereby the second capacitor creates a zero in the frequency response of the amplifier to compensate for a pole produced by any capacitive load coupled to the second output.