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Magnetic Core Multivibrators

IP.com Disclosure Number: IPCOM000098146D
Original Publication Date: 1960-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Neff, GW: AUTHOR [+3]

Abstract

A magnetic core, made of material capable of attaining different stable states of flux remanence and exhibiting a large saturation slope, is utilized for coupling two transistors to provide a multivibrator capable of monostable, bistable and astable types of operation.

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Magnetic Core Multivibrators

A magnetic core, made of material capable of attaining different stable states of flux remanence and exhibiting a large saturation slope, is utilized for coupling two transistors to provide a multivibrator capable of monostable, bistable and astable types of operation.

When T(1) conducts, its collector current drives the core into the 0 state. Conduction of T(2) drives the core into the 1 state. The -V(b) is the base biased supply necessary to hold both T(1) and T(2) off. R(e) is a current limiting resistor to maintain proper power dissipation in the transistors during conduction.

Assuming the core is in the 1 state and a voltage pulse is applied to P(1), T(1) is triggered into conduction and as I(c1) begins to flow, the core starts switching to the 0 state to induce a voltage in N(1). This action holds T(1) in conduction until switching of the core is complete. If a similar pulse is afterwards applied at P(2), the blocking oscillator action occurs on the T(2) side of the circuit and the core is switched to the 1 state. A current spike at the end of I(c1) exists because T(1) has been saturated and maintains current flow after the core has completed switching, while the switching resistance of the core winding N(3) disappears.

This current spike produces a flux change in the core because of the large saturation slope of the material. Considering the saturation slope as being represented by an inductance L, the induced voltages in the windings of the core while in the saturated region will be e = L*di(c)/dt. The rate of increase of collector current during this spike is less than the rate of decrease and, therefore, L*di(c)/dt is greater during the decay of the current spike. For this reason there is an overshoot in the voltage waveform of v(b1), v(cl), v(b2) and v(c2).

For the two-input bistable operation of the circuit described above, the voltage overshoot of v(b2) must be limited so that it does not trigger T(2). It is then possible to choose the feedback winding N(2) such...