A bipolar linear transconductor using translinear cells and its application

Abstract

A novel linear transconductor using translinear cells is proposed. It consists of a voltage follower, a resistor, and a current follower. SPICE simulations using an 8 GHz bipolar transistor-array parameter show that the linear transconductor with a transconductance of 1 mS exhibits a linearity error of less than +/- 0.75% over an input voltage range of +/- 1 V for a supply voltage of +/- 2.0 V. The temperature coefficient of the transconductance is less than 124ppm/degrees C. The -3-dB frequency of the transconductance is more than 4.5 GHz. Applying the linear transconductor as a building block, the design of a bandpass filter with center frequency of 85 MHz and Q-factor of 80 is presented.