Amplifiers with wide input range and low input capacitance

A method of amplification with wide input range and low input capacitance, the method comprising:

• receiving a differential input signal between a pair of input terminals;
• selecting a pair of n-type input transistors or a pair of p-type input transistors for amplifying the differential input signal based on an input common-mode voltage of the pair of input terminals, the pair of p-type input transistors including a first p-type input transistor and a second p-type input transistor;
• opening a first pair of isolation switches to decouple the pair of n-type input transistors from the pair of input terminals when the pair of n-type input transistors is not selected;
• and
• opening a second pair of isolation switches to decouple the pair of p-type input transistors including both the first p-type input transistor and the second p-type input transistor from the pair of input terminals when the pair of p-type input transistors is not selected.

An amplifier comprising:

• a pair of input terminals configured to receive a differential input signal, wherein the pair of input terminals has an input common-mode voltage;
• and
• an amplifier input stage comprising:
• a pair of n-type input transistors, and a pair of p-type input transistors including a first p-type input transistor and a second p-type input transistor;
• a first pair of isolation switches connected between the pair of n-type input transistors and the pair of input terminals, and a second pair of isolation switches connected between the pair of p-type input transistors and the pair of input terminals;
• and
• a control circuit configured to open the first pair of isolation switches and close the second pair of isolation switches over a first range of the input common-mode voltage, and to open the second pair of isolation switches and close the first pair of isolation switches over a second range of the input common-mode voltage, the control circuit further configured to disconnect both the first p-type input transistor and the second p-type input transistor from the pair of input terminals over the second range of the input common-mode voltage.