Final answer:
The main characteristic of the input stage in a multistage voltage amplifier is high input resistance, which prevents signal loss from the source.
Step-by-step explanation:
In a multistage voltage amplifier, the main characteristic of the input stage is high input resistance. This characteristic is crucial because it allows the amplifier to not load the preceding circuit or source driving the amplifier, thus avoiding signal attenuation. High input resistance helps ensure that the maximum amount of signal is transferred into the amplifier for processing. It should be noted that while other characteristics such as high voltage gain and low output resistance are also important in an amplifier's design, they are typically associated with later stages of the amplifier. For instance, high voltage gain is usually the main feature of intermediate stages, whereas low output resistance is characteristic of the output stage to allow better power transfer to the load.