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NEGATIVE TRANSIENT SIGNAL SWITCHING CIRCUIT

IP.com Disclosure Number: IPCOM000005916D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2001-Nov-15
Document File: 1 page(s) / 54K

Publishing Venue

Motorola

Related People

Wayne Bates: AUTHOR

Abstract

When testing the durability of electronic products under conditions of severe electrical stress, it is often necessary to inject large negative transient test voltages through a specified test impedance into the positive power input terminals of the unit under test. Historically this has been done with either a switching relay, which has the disadvantages of slow actuation and contact bounce, or an isolating transformer in series with the power source, which has the disadvantage of being incapable of handling pulses longer than a few milliseconds. Solid state transistor switches are not a satisfac- tory solution, because transistors with sufficient current and voltages ratings are too slow for microsecond range pulses.

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MOTOROLA Technical Developments Volume 10 March 1990

NEGATIVE TRANSIENT SIGNAL SWITCHING CIRCUIT

by Wayne Bates

   When testing the durability of electronic products under conditions of severe electrical stress, it is often necessary to inject large negative transient test voltages through a specified test impedance into the positive power input terminals of the unit under test. Historically this has been done with either a switching relay, which has the disadvantages of slow actuation and contact bounce, or an isolating transformer in series with the power source, which has the disadvantage of being incapable of handling pulses longer than a few milliseconds. Solid state transistor switches are not a satisfac- tory solution, because transistors with sufficient current and voltages ratings are too slow for microsecond range pulses.

This circuit uses a power supply amplifier and a diode switching circuit to provide both the DC power and the negative transient signal.

   Figure 1 shows an ordinary function generator (1) which is capable of generating the required transient teat waveform. This generator drives the power supply amplifier (Z), which has a frequency response range down to and including DC. In operation, the function generator initially supplies a DC voltage which is amplified and conducted through a fast recovery power diode (3) to provide the proper operating voltage for the unit under test (4). This is Vpwr in Figure 2. At time tr the generator outputs...