Design Of An Enhanced Translinear Variable Floating Resistor And Its Application In A VGA

Abstract

An improved current controlled floating resistor is designed based on translinear loops for application in a Variable Gain Amplifier (VGA). This work compares the use of two different devices and evaluates the difference based on the model parameters and circuit performance. The different architectures employed clearly demarcate the performance variations. The translinear variable resistor exhibits a dynamic range greater than 60 mV. The resistance value lies in the range of 3 KΩ to few Ohms. A Current Feedback Operational Amplifier (CFOA) is also designed to have an f -3dB of 250 MHz. The CFOA together with the variable resistor in a difference amplifier configuration constitutes a VGA with a variable voltage gain in the range of 1 to 10. The circuit's intended applications involve front-end of communication systems, temperature sensors, filters etc. The circuit has been implemented using National's VIP10 process, which caters to the high speed bipolar technology. Measurement results obtained are a good reflection of the various factors that affect the performance and show a good amount of compliance to that of the simulated results.