Philips Electronics North America Corporation

Ronald Hogervorst

Johan Hendrik Huijsing

John P Tero

A rail-to-rail input stage with constant g.sub.m and constant common-mode output currents is provided. The common-mode output currents are controlled by the use of current switches. When low and high common-mode input voltages are applied to the input stage, the current switches take part of the tail currents of the input stage transistors, divides it into two equal parts, and directs the two equal current signals to the outputs. When intermediate common-mode input voltages are applied, the current switches regulate the tail currents of the input pairs such that the common-mode output current and g.sub.m remains constant. The current switches are responsive to changes in the common-mode input voltages, and thereby maintain the g.sub.m constant.

Rail-to-rail input stages with constant g.sub.m and constant common-mode

Compact g.sub.m -control circuits for CMOS rail-to-rail input stages operating in strong inversion are provided. The G.sub.m -control circuit makes the sum of the gate-source voltages of the complementary input transistors, and therefore the g.sub.m of the input stage constant. The compact g.sub.m -control circuits implement a floating voltage source in the form of circuit elements between the N and P-channel input stage transistors and the positive and negative supply rails of the operational amplifier.

Compact GM-control for CMOS rail-to-rail input stages by regulating the

A transconductance (g.sub.m) control circuit for bipolar or CMOS rail-to-rail input stages is provided. The g.sub.m is controlled by the use of multiple input pairs and can be used in CMOS or bipolar technology. In CMOS the g.sub.m -control works regardless of the operating region of the MOS transistor, whether it is weak, moderate or strong inversion.

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Voorschoten, Netherlands

Ronald Hogervorst