a telescopic cascode operational amplifier fig9 illustrates another embodiment of the operational amplifiers 310 410 and 510 the circuit of fig9 is referred to as a folded cascode operational amplifier the right half of the operational amplifier 900 includes 4 stacked transistor groups the 4 transistor groups from top to bottom includes a pmos 930 and a pmos 935 a pmos 940 and a pmos 945 a nmos 950 and a nmos 955 as well as a nmos 960 and a nmos 965 respectively the gates of the 4 transistor groups are respectively biased by voltages v b1 v b2 v b3 and v m the left half of the operational amplifier 900 includes another transistor group made up of an nmos 920 and an nmos 925 the drains of the nmos 920 and the nmos 925 are respectively coupled to the drain of the pmos 930 and the drain of the pmos 935 their sources are both coupled to a current source 910 and their gates serve as the inputs of the operational amplifier 900 the pmoss in the operational amplifiers 600 700 800 and 900 can be substituted by nmoss and vice versa and the same function can be obtained with correspondingly adjusted polarities and biases such modifications are well known to people having ordinary skill in the art and therefore are omitted for brevity fig1 illustrates a flowchart of a sampling method according to.