Research Of Programmable Gain Amplifier And Automatic Gain Control Circuit

At present, digital broadcast receivers are gradually replacing analog ones. The digital radio standards are DAB, DRM, DMB, etc. The DRM system is designed for the signal whose spectrum is under 30 MHz. It is mainly used to handle long wave, medium wave and short wave. The DAB system is designed for the radio signal whose spectrum is between 30 MHz and 3 GHz. For the receivers designed according to the DRM and/or DAB standards, automatic gain control system often plays an important role.This paper introduces the automatic gain control system architecture first. Then, this paper compares the advantages and disadvantages of two different architectures. To satisfy the application situation, the feedback architecture is accepted. Then, the internal modules of the architecture, such as programmable gain amplifier, DC offset cancellation, received signal strength indication, etc, are discussed and the key details of the design, are descripted. These details often determine whether the chip can work successfully. At last, the pin reuse in layout design is discussed, and the test results are analyzed, and the solution to the problem is presented.The chip is fabricated with SMIC’s 180-nm CMOS process. This design contains programmable gain amplifier, rectifier, gain control word generator, DC offset cancellation, oscillator and low pass filter circuit. According to the given design goal, this paper designs a specific circuit, layout, and provides the relevant pre-simulation and post-simulation results. The chip test results show that the power supply voltage is 1.8 V. The chip can normally handle the signal whose frequency is 2.048 MHz. The target of design is fulfilled. The total current of the chip is 1.9 mA. The regulating range is 10-50 dB, and the gain step length is about 1 dB. The output offset voltage of the system is reduced to less than 20 mV.After testing the modules one by one, the paper gives the explanation of testing results. At the same time, the cause of each problem is analyzed and the solution is given. The further research direction is proposed.