Design of high-side current sense amplifier with ultra-wide ICMR

A high-side current sense amplifier with wide input common mode range (ICMR) is proposed. To improve the accuracy of signal transfer, a common base structure is introduced to realize the control to bias currents. And a high accurate current mirror is used to enhance the gain precision. In addition, a common emitter and common source class AB amplifier topology is proposed to provide a rail-to-rail output and high driven capability. As results, the amplifier keeps the constant closed-loop voltage gain of 50 V/V, and an ICMR of 0 V-28 V is achieved, which is independent of the supply voltage. It can work at low supply voltage down to 1.5 V. And the minimum supply current is 38 muA. The chip was designed and fabricated in 1.5 mum BCD technology. The experimental results showed that the chip works normally and all expected specifications are achieved.