A 77-dB Dynamic Range Low-Power Variable-Gain Transimpedance Amplifier for Linear LADAR

An adjustable-gain transimpedance amplifier with a wide linear dynamic range, low power consumption, and low input impedance was designed for a pulsed linear laser detection and ranging system. To extend the linear dynamic range within a low power consumption, some specific techniques are presented. A low-power current-mirror amplifier with a level shifter was used to decrease the input impedance and keep it stable. Adjustable transimpedance gain extends the input dynamic range, and a high-pass filter eliminates the influence of dc operating point drift caused by the variable gain. When implemented in 0.18-mu m standard CMOS technology, the receiver achieved a high gain of 106 dB with four configurable gain modes, a wide linear output swing of 1 V, an input-referred noise current of 1.52 pA/root Hz, and a minimum detectable signal of 400 nA at SNR = 5, leading to a linear dynamic range of 77 dB, and the power consumption in the highest gain mode was 8 mW with a 3.3-V supply.