Transistors [M.sub.r1] and [M.sub.r2] biased in the linear region implement a current divider which realizes transconductance tuning expressed as 
Accordingly, in the proposed implementation of the constant-C tuning technique, switching the binary weighted transconductor arrays [G.sub.m3] and [G.sub.m4] sets the frequency range, while variation of the unit transconductance via the current divider [M.sub.r1_Gm3,4]-[M.sub.r2_Gm3,4] implements fine-tuning of the lower cutoff frequency, following equation
Connecting the source contacts of, say, 1 in 1000 cells together and providing a separate sensing source connection, the device operates as an accurate high-ratio current divider
provided that the sensing source and main source connections operate at the same potential.
It is designed, simulated and fabricated using a 0.18om 1P6M CMOS technology.The fabricated current-mode AGC chip consists of a current peak detector, a current subtractor, a circuit which consists of a square current generator and a current divider
. The circuit is followed by a current squaring circuit, a current inverter and an analog current multiplier.The utilization of this fabricated AGC chip--in current-mode RF receiver systems, hearing aid instruments and television tuners--will contribute to reducing the power consumption of such systems, which consequently reduces their need for high capacity batteries.