Low power CMOS fully differential variable-gain amplifier

This paper presents the design, analyses and measurement results of a fast differential variable-gain amplifier (VGA) intended for high-speed data streaming applications such as the IEEE 802.11a wireless LAN. The circuit is a seven stage amplifier that offers a programmable gain in the 0divide84 dB range, in 6 dB steps. Each stage has a programmable gain of either 6 dB or 12 dB. Fully differential low power opamps are used. With an opamp gain-bandwidth product (GBW) of about 200 MHz, the input frequency can go as high as 10 MHz. Offset filtering is possible with a high pass filter with programmable 3 dB frequency. The circuit operates at only 2.5 V, making it an ideal choice for low-power mobile applications. The VGA is fabricated in a 0.13 mum standard analog CMOS technology. It occupies 0.18 mm² and the typical power dissipation is about 7.5 mW