The ideal maximum voltage for a common drain amplifier is 1.

Explanation:
A common drain amplifier, also known as a source follower, is a type of amplifier where the output is taken from the source terminal of the MOSFET. It is commonly used to provide impedance matching between high and low impedance circuits.

In a common drain configuration, the gate terminal is the input, the source terminal is the output, and the drain terminal is connected to the power supply. The voltage gain of a common drain amplifier is less than 1, which means the output voltage follows the input voltage with a slight attenuation.

The maximum voltage that can be applied to the input of a common drain amplifier is limited by the maximum allowable voltage for the MOSFET. This maximum voltage is usually specified in the datasheet of the MOSFET and is referred to as the Vgs(max) rating.

The Vgs(max) rating represents the maximum voltage that can be applied between the gate and source terminals of the MOSFET without causing damage. If the input voltage exceeds this maximum rating, it can lead to breakdown of the gate oxide layer and permanent damage to the device.

Therefore, the ideal maximum voltage for a common drain amplifier is the Vgs(max) rating of the MOSFET used in the circuit. Typically, this value is around 1V for most MOSFETs, hence the correct answer is option B (1).