Abstract: CMOS integrated circuit buffers typically use a dual-diode electrostatic discharge (ESD) protection technique. However, in some cases that technique inadvertently causes one of the diodes to conduct when a desired signal voltage is present on the bondpad, thereby clipping the desired signal. This occurs, for example, when an output buffer on an unpowered device is connected to an active bus, or when the input buffer of a 3 volt device receives a 5 volt signal. The present invention solves this problem by using a bipolar (e.g., pnp) protection transistor connected between the bondpad and a power supply bus (e.g., V.sub.SS). The base of the transistor is connected to the bondpad through a resistor that provides a time delay due to the R-C time constant that includes distributed capacitance. The time delay allows for a high conduction period, during which an ESD event is conducted through the bipolar transistor, thereby protecting the input or output buffer.

Abstract: A circuit is disclosed which converts CMOS logic input signals to ECL output signals. A pair of FETs, arranged as a conventional CMOS inverter, responds to the CMOS logic input signals and drives a bipolar transistor operating as a voltage follower. The emitter of the bipolar transistor serves as the output of the buffer providing the ECL output signals. A resistor having a predetermined resistance couples between a voltage source and the base of the bipolar transistor. First one of the pair of FETs couples a constant current source to the resistor and the base of the bipolar transistor when the buffer is supplying an ECL logical "zero" logic signal. The current from the current source passing through the resistor establishes the ECL logical "zero" output voltage. Second one of the pair of FETs shunts the resistor when the buffer is supplying an ECL logical "one" output, allowing faster transitioning of the output of the buffer from an ECL logical "zero" to a logical "one".

Abstract: An integrated circuit comprises a resistor that is formed by doping a semiconductor region that is defined by a layer, typically polysilicon, that also defines the gate electrode of field effect transistors in the integrated circuit. The well-controlled linewidth of features defined in this layer provides for tight resistor tolerance, and also allows the value of the resistor to track changes in other features defined by this layer.

Abstract: In various analog applications, it is desirable to have a known offset voltage at the input of a comparator, operational amplifier, or other type of differential stage. For example, in an ISDN receiver, the use of a desired offset allows for discriminating between signals having different amplitudes. In the present technique, a reference current, derived from a reference voltage (V.sub.ref) and on-chip resistor (R1) is used to set the currents through two input transistors, typically MOS transistors. An offset resistor (R0) in the source lead of one of the transistors produces a voltage drop that sets the offset at an input of the differential stage. The voltage drop across R0 is proportional to (V.sub.ref .times.R0)/R1. Since R0 and R1 are fabricated by the same process, their ratio is independent of temperature, process, etc. Therefore, a well-defined offset is obtained.

Abstract: A field effect transistor circuit generates a reference current that can obtain a desired temperature coefficient. The circuit is self-compensatory with respect to process variations, in that a "slow" process will produce a higher than normal current, while a "fast" process will give a lower one. This results in a tight spread of slew-rate, gain, gain-bandwidth, etc. in opamps, comparators, and other linear circuits. A simple adjustment in the circuit allows the temperature coefficient to be made positive or negative if so desired. An illustrative circuit is shown for CMOS technology, but can be applied to other field effect technologies.

Abstract: A process for making dielectrically isolated silicon integrated circuits which use silicon oxide filled trenches to provide isolation is described. To minimize damage to the silicon, the trenches are filled by sequentially annealed oxidation process which involves alternately growing some oxide and then annealing to relieve stresses before growing more oxide.