Elantec, Inc.

Edward C Bee

Douglas S Smith

Stephen F Colaco

An integrated active filter and sync separator circuit operates on precision internal reference sources to set the filter cut off frequency as a function of resistance of an external resistor. The active filter eliminates the source of sync tip crushing attributable to conventional clamping circuits associated with sync pulse detectors, and also provides sync pulses substantially devoid of time-variant jitter.

Synchronizing signal active filter and method

A class AB complementary output stage provides maximum output voltage swings and high load currents with minimum power dissipation. The output stage includes a first bias circuit that generates a pair of voltage nodes with a resistor controlled bias current. A second bias circuit comprises four current sources the outputs of which are coupled pair-wise across a resistor to form a pair of high impedance nodes at the resistor terminals. The voltage nodes of the first bias circuit establish bias currents in a differential input stage and in a pair of current sources of the second bias circuit. The outputs of the differential input stage drive the inputs of second pair of current sources in the second bias circuit, which provide drive current to the high impedance nodes. The output circuit comprises a pair of complementary common source transistors, the gates (bases) of which are driven by the high impedance nodes of the second bias circuit.

Class AB complementary output stage

An active folded cascode includes an amplifier transistor and a source follower transistor configured as a folded cascode with the drain of the amplifier transistor and the source of the follower transistor connected to form a gain node. A feedback transistor has its gate and drain connected to the source and gate of the follower transistor while bias current provided to the drain of the feedback transistor by a current source maintains the gain node at a fixed voltage with respect to a reference voltage. Coupling of the voltage at the gain node to the gate of the source follower transistor by the feedback transistor reduces the effective source impedance of the source follower transistor, providing improved gain and bandwidth properties for the active folded cascode circuit.

Active folded cascode

A multiplexer circuit includes pairs of control elements such as CMOS transistors serially connected between common circuit nodes to conduct current therebetween in response to one of each pair of control elements being selectively biased to conductive or non-conductive states by an applied control signal. The current enabled to flow between circuit nodes through a pair of control elements biased to conductive state is determined by the magnitude of an applied signal, and a current-difference circuit compares the current flowing between circuit nodes with a reference current to produce an output signal representative of the applied signal which is selected in response to an applied control signal.

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San Jose, CA, United States of America

Edward C Bee