A variable gain CMOS amplifier with exponential gain control

A variable gain amplifier architecture suitable for foundry CMOS is constructed using linearized transconductance blocks. The use of a four-transistor transconductance cell allows for wider gain range and larger signal swing under low supply conditions than the simple differential pair used in previous work. Experimental results with 0.6 /spl mu/m CMOS show -5 to 35 dB gain and 20 MHz bandwidth at 21 mW.