A low power, low noise, variable gain amplifier

A variable gain amplifier has been applied in a monolithic television system for amplification of IF signals and was realised in a BiCMOS process. The amplifier has a gain range from -7dB to 66dB. The dynamic range at minimum gain is equal to 68dB where the THD is lower than -66dB for an output signal of 100mVRMS. The power dissipation is 10mW at a 5V supply voltage. Amplifiers with such a large gain range usually consist of multiple stages. In this concept gain stages are shunted if these are not needed for a specific amplification which results in a negligible noise and distortion contribution of these stages. In combination with a smart gain stage topology a high dynamic range at low power can be achieved.