CMOS exponential-control variable gain amplifiers

New CMOS exponential-control variable-gain amplifiers (VGAs) are presented. The control signal can be either current-mode or voltage-mode. Since no multiplier is needed in the proposed circuits, the proposed VGAs can be very compact. For the case of supply voltages V_DD=|V_SS|=1.5 V, the power dissipation is only 0.48 mW. The gain control range of the proposed VGA can be 30 dB. The proposed circuits have been fabricated in a 0.5 μm n-well CMOS process. Experimental results are given to confirm the feasibility of the proposed VGAs, which are expected to be useful in analogue signal processing applications.