Abstract: A method is disclosed for preparing novel PNA synthons having protecting groups capable of removal under mild conditions. The PNA synthons are prepared by coupling novel N-substituted nucleobase intermediates having carbamate protection of the exocyclic amino group of the heterocycle to an amino protected backbone or an amino protected backbone ester of the amino acid N-(2-aminoethyl)-glycine. By the method of this invention, the resultant PNA synthons can have orthogonal protection of the carbamate protected nucleobase and the amino protected backbone. The PNA synthons are useful in the synthesis of peptide nucleic acids (PNAs) and other oligomers such as PNA-DNA chimeras, and may be used in automated synthesizers. Novel compositions of matter are also disclosed. In addition, a guanine PNA synthon having selective carbamate protection of the exocyclic 2-amino group with the C6 carbonyl group unprotected is disclosed.

Abstract: A method is disclosed for preparing novel purine PNA synthons having protecting groups which may be removed under mild conditions. The purine PNA synthons generally are prepared by coupling purine derivatives having carbamate protection to a protected N-(2-aminoethyl)-glycine backbone. By a method of this invention, purine PNA synthons may have orthogonal protection of the carbamate protected purine and the protected backbone. The purine PNA synthons are useful in the synthesis of peptide nucleic acids (PNAs) and other oligomers such as PNA-DNA chimeras, and may be used in automated synthesizers. In practicing methods of the invention, novel compositions of matter also are disclosed.

Abstract: A low voltage constant transconductance input stage is achieved with relatively simple design methodology. The approach uses current-mode techniques and is based upon the processing of signal currents, rather than handling the bias currents of input stages. Such an approach becomes universal and independent of the input stage transistor types (FET or bipolar) and their operating regions. Further, the arrangement considerably simplifies the design procedure of low voltage operational amplifiers. MOS and bipolar Op Amp input stages are described wherein almost constant g.sub.m is achieved which is independent of the common mode input voltage ranging from rail-to-rail.

Abstract: The reduction of the power supply voltage of VLSI circuits to 3.3 volts results in a significant loss in input and output swing in traditional CMOS analog circuits. In order to achieve rail-to-rail operation, n-channel and p-channel MOSFETs are placed in parallel so that at least one type of transistors are operating in a high gain region throughout the entire input range. However, circuit characteristics change as transistors turn on and off. A constant transconductance bias means enables the rail-to-rail CMOS differential stage to possess a constant transconductance over the entire common mode voltage range. Significantly, the bias circuit does not require any matching between the transistors of opposite types.

Abstract: A circuit apparatus suitable for use as a basic building block of very small geometry integrated circuits (on the order of 1 micron and smaller) comprising (i) a current mirror circuit with a cascode output, comprising a first transistor and a second transistor connected in series, the first transistor coupled between a ground and the second transistor, and (ii) a single stage gain loop comprising a transresistance amplifier coupled between a control input of the second transistor and the series connection of the first and second transistors, wherein the circuit apparatus provides an output with high impedance output and with maximum swing capability.

Abstract: A voltage to current converter includes three field effect transistors (FETs), the sources of which are electrically connected to define a common source node, and a feedback network. First and second voltage inputs are connected to the gates of the first and second FETs, respectively. First and second current outputs are connected to the drains of the first and second FETs, respectively. The feedback network is connected between the drain of the third FET and the common source node. The feedback network controls and extends linearity by varying the voltage between the common source node and ground in response to changes in the voltage inputs in order to maintain a constant current through the third FET. The floating common source node quickly adjusts and thereby keeps a linear relationship between the input voltages and the output currents. Thus, the feedback network can dynamically bias the converter by permitting the common source node to float with respect to ground.

Abstract: A system for spraying ceramic coatings on surfaces in contact with molten metals in which a constant amount of slurry made from water and ceramic powder is supplied to a pump and a hose for applying the slurry to the surface to be coated. Activation of an air valve delivers air to the hose at a sufficient pressure to spray the slurry on the surface to be coated. Deactivation of the air valve shuts off the pump.