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Voltage Controlled Multivibrator

IP.com Disclosure Number: IPCOM000086926D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Hong, JH: AUTHOR [+2]

Abstract

The voltage-controlled multivibrator (VCM), shown in the figure, differs from prior circuits by the ability to accept digital input(s), and provides a filter function while maintaining temperature and power supply insensitivity.

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Voltage Controlled Multivibrator

The voltage-controlled multivibrator (VCM), shown in the figure, differs from prior circuits by the ability to accept digital input(s), and provides a filter function while maintaining temperature and power supply insensitivity.

The VCM circuit includes a "control section" with a passive filter which accepts logic-level input directly from the phase comparator. The control section provides a "Logic In - Logic Out" function, requiring only a digital phase comparator to form a phase-locked loop, whereas prior circuits depend on a "drift-less" analog filter and driver. To accommodate a two-output phase comparator, an additional current switch (like T17, T18 and T19) may be provided. The collector of T18 is connected to the collector of the corresponding transistor in the additional current switch.

In addition, a current switch T15-T16 has been added to the prior circuit, causing it to latch and, thereby, avoiding potential circuit malfunctions associated with stray elements at I/O's C1 and C2. This latching feature also causes the circuit to operate as a set-reset latch (with nonstandard inputs), enabling the oscillator output to be toggled by forcing the timing capacitor I/O's C1 and C2 with or without external components in place. Such a feature would be useful for LSI testing, if the clock (oscillator) were not directly available, or could not be forced.

Circuit operation is as follows: A filter capacitor (not shown), possibly in series with a resistor, is connected between ground and the I/O CAP to determine the parameters in the filter transfer function, (1 + srT)/(1 + sT). An adjustable resistor (not shown) is connected between...