A Multichannel,high Dynamic Range And Low Noise Variable Gain Amplifier Design

A VGA(Variable Gain Amplifier)with a multi-channel,high gain value dynamic range and low noise characteristics has emerged,in the detection of bioelectronic signals.There is often a need to detect and process multiple signals simultaneously,the strength of the detected signals may be greatly different,due to its own source,the different propagation paths,and so on.In this paper,a VGA with a multi-channel,high gain value dynamic range and low noise characteristics is designed.First of all,the working principle of the AGC(Automatic Gain Control)is discussed,and then the implementation of the cascade of PGA(Programmable Gain Amplifier)is designed.In the design of this system,the VGA consists of two parts: the coarse gain stage and the fine gain stage.The coarse gain stage can be further divided into an amplification gain stage and an attenuation gain stage,each part being cascaded by 4 fully differential transconductance enhanced amplifiers with a source stage negative feedback resistor.The amplification part has a gain value of 15 dB,and the attenuation part has a gain value of-15 dB.So the coarse gain stage can be controlled in the range of-60dB~60dB with a step value of 15 dB.The fine gain stage has a gain value range of 0~15.5dB with a step of 0.5dB.Then,the logical part is designed.The combination of a 4-way to 16-way decoder and switches completes the selection of 16 channels,and two 3-way to 5-way decoders and a 5-way to 32-way decoder combined with switches are used to achieve the selection of gain values.At last,the design of the layout and post-simulation of this system were completed.The area of layout is 3mm×1.6mm.This system was built in TSMC 0.18?m CMOS process and simulated in the Spectre simulation environment.According to the post-simulation results,the gain value ranges from-60.4dB to 74 dB with a step value of 0.5dB,the equivalent input noise is 8.43?V(10Hz~30kHz),and the IP3(3rd order Intercept Point)is 3.52 dBm,the power consumption is 1.9mA of single channel.It can be seen that,the 16-channel VGA designed with high dynamic range and low noise characteristics meets the specifications.