Patent ID: 7015758

Claim:
A gain control circuit comprising: a control voltage supply circuit using an external control voltage to generate an internal control voltage; and a variable gain circuit having an uncompensated gain characteristic and a compensated gain characteristic, wherein: said control voltage supply circuit generates said internal control voltage in response to said external control voltage as to compensate for linearity of said variable gain circuit to an extent of said external control voltage where said variable gain circuit loses said linearity, said internal control voltage relative to said external control voltage from a first reference voltage to a second reference voltage is different from when said external control voltage is less than said first reference voltage or exceeds said second reference voltage, said uncompensated gain characteristic relative to said external control voltage is linear from said first reference voltage to said second reference voltage, and is non-linear when said external control voltage is less than said first reference voltage or exceeds said second reference voltage, said variable gain circuit uses said internal control voltage to produce a compensated gain characteristic, said compensated gain characteristic relative to said external control voltage being linear from said first reference voltage to said second reference voltage, and being linear when said external control voltage is less than said first reference voltage or exceeds said second reference voltage, and said compensated gain characteristic is a transmission gain.