Cmos transconductance amplifier having floating operating point


PURPOSE: To facilitate an good operation, to obtain a high output current, and to reduce the power consumption by disregarding a steady positive current of an output transistors(TR), regardless a high overall conductance when no load current is supplied to the amplifier. CONSTITUTION: An input stage of an amplifier is provided with a voltage-current converter u 1 , consisting of transistors(TRs) t 1 , t 2 and receives an input voltage (u) as a voltage difference. The converter u 1 distributes a current supplied at a current supply point S into currents u 1 , u 2 . Currents i 1 , i 2 are obtained at nodes A, B, and a weight ratio depends on the voltage (u). TRs t 3 , t 4 form a p-channel mirror. An output current of the TR t 2 and an active load a 1 at the node A form a difference between the currents i 1 , i 2 . The node A provides a current output of the u 1 , with respect to a current difference i d . The current i d is extracted by a current mirror p 1 . A current i 0 given to a current supply point S forms a current bank n b . TRs t r , t 7 form an output node to provide a load current i. The transconductance of the amplifier is adjusted by W/L of the TRs t 1 , t 2 , t r , t a and the current i 0 . COPYRIGHT: (C)1992,JPO




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