Abstract
A broadband linear-in-dB variable-gain amplifier (VGA) circuit is implemented in 0.18 μm SiGe BiCMOS process. The VGA comprises two cascaded variable-gain core, in which a hybrid current-steering current gain cell is inserted in the Cherry-Hooper amplifier to maintain a broad bandwidth while covering a wide gain range. Postlayout simulation results confirm that the proposed circuit achieves a 2 GHz 3-dB bandwidth with wide linear-in-dB gain tuning range from −19 dB up to 61 dB. The amplifier offers a competitive gain bandwidth product of 2805 GHz at the maximum gain for a 110-GHz ftBiCMOS technology. The amplifier core consumes 31 mW from a 3.3 V supply and occupies active area of 280 μm by 140 μm.
Highlights
The telecommunication industry continues to drive forward with gigabit-class high-speed data transmission in microwave, millimeter-wave, and optical communication systems
variable-gain amplifier (VGA) as a key component in the automatic gain control (AGC) loop provides constant signal strength to the baseband processor to maximize the dynamic range of the receiver system and compensates gain variations caused by process, voltage, and temperature (PVT) variations
The VGA occupies 280 μm by 140 μm and total chip with testing pads takes an area of 800 μm by 550 μm
Summary
The telecommunication industry continues to drive forward with gigabit-class high-speed data transmission in microwave, millimeter-wave, and optical communication systems. VGA as a key component in the automatic gain control (AGC) loop provides constant signal strength to the baseband processor to maximize the dynamic range of the receiver system and compensates gain variations caused by process, voltage, and temperature (PVT) variations. Solutions employing CherryHooper amplifier [8] can achieve a 3-dB bandwidth above 2 GHz and satisfy bandwidth requirements such as 60 GHz short-range wireless systems. Their gain range is not sufficient to meet the target of more than 80 dB if additional margin is needed for the receiver. A linear-in-dB control signal for VGA will simplify the system level design for AGC
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