Patent Number: 6,166,569

Title: Test interface circuits with waveform synthesizers having reduced spurious signals

Abstract: Waveform synthesizers are disclosed that generate an output signal S.sub.OUT with independent response to a common-mode input signal S.sub.CM, an input data signal S.sub.D and a current programming signal S.sub.PRGM. The synthesizers include a differential pair of first and second transistors that respectively respond to the input data signal S.sub.D and to a fixed reference signal V.sub.REF. Because the second transistor is referenced to a fixed potential, current-pumping action of parasitic capacitances is reduced with consequent reduction of transient signals in the output signal S.sub.OUT. Signal transients are further reduced with diodes that are arranged to block transient-current interchange between the first and second transistors. To enhance synthesizer speed, known bias potentials are established in the first and second transistors by use of a keep-alive current source, a bias transistor and a bias resistor and thermal differential heating in the differential pair is reduced with cascode transistors. The synthesizers are especially suited for use in ATE interface circuits.

Inventors: McQuilkin; Christopher (Salem, NH)

Assignee: Analog Devices, Inc.

International Classification: G01R 31/28 (20060101); G01R 31/319 (20060101); H03B 021/00 ()

Expiration Date: 12/26/2017