A CMOS LINE DRIVER WITH 80-DB LINEARITY FOR ISDN APPLICATIONS

A high-performance CMOS line driver for ISDN U-interface transceiver applications has been designed and fabricated. Careful study of requirements and trade-offs affecting linearity, power efficiency, and quiescent current presented in this paper has resulted in a circuit structure featuring a highly linear input/output characteristic and well-controlled quiescent current. The prototype line driver is capable of delivering a 5V(pp) signal of up to 80 kHz to a 60-OMEGA load while exhibiting linearity in the order of 77 +/- 5 dB and operating from a single 5-V power supply. Linearity better than 70 dB is maintained for load resistances as low as 20-OMEGA.