A CMOS relative ultrasound energy measurement circuit with temperature compensation

A CMOS temperature compensated circuit used in measuring relative ultrasound energy is presented in this paper. The core of the circuit is a temperature compensated voltage to current squarer (VCSQ) and a current integrator. The VCSQ consists of a Linear-Transconductor(LTC) and a current-mode squarer. A current source (dependent on MOS transconductance which is in turn dependent on absolute temperature) is used to bias the current-mode squarer; this provides temperature compensation of the circuit. The circuit is simulated for AMI05 (0.5um) technology using Eldo in Mentor Graphics environment. With the compensation, the VCSQ output drift with temperature is achieved better than 1.98% in the 10~90°C range for ±1.2V input range. The integrator output drift is achieved for full scale error better than 2.5% in the 10-90°C range, 1.6% in the 30~90°C range.