Browse Prior Art Database

Fast Position Feature for a CRT Display Incremental Stroke Generator

IP.com Disclosure Number: IPCOM000050500D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Marple, WP: AUTHOR

Abstract

The figure illustrates an incremental stroke generator circuit for deflecting the electron beam of a CRT display. In the prior art, a digital to analog converter would convert the digital input to the incremental analog output for each incremental vector to be displayed. In order to smooth out the initial spike in the analog waveform for each incremental step, a conventional diode bridge consisting of the diodes D1 through D4 was connected between the digital to analog converter and the output amplifier A1.

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Fast Position Feature for a CRT Display Incremental Stroke Generator

The figure illustrates an incremental stroke generator circuit for deflecting the electron beam of a CRT display. In the prior art, a digital to analog converter would convert the digital input to the incremental analog output for each incremental vector to be displayed. In order to smooth out the initial spike in the analog waveform for each incremental step, a conventional diode bridge consisting of the diodes D1 through D4 was connected between the digital to analog converter and the output amplifier A1.

The problem with the prior-art circuit is that a large-scale displacement across the face of the CRT cannot be done at a rapid rate since the maximum slew rate capable of being input to the amplifier A1 is the current I divided by the capacitance C of the capacitor connected between the input of the amplifier Al and ground potential.

This problem is solved by the addition of the diodes D5 and D6, as shown. When relatively low magnitude amplitude signals are output from the digital to analog (D/A) converter for the production of small incremental vectors, the diodes D5 and D6 are in their off state, since these voltages are less than the turn-on voltages for the diodes D5 and D6. However, when a large-scale displacement is desired to be made on the face of the CRT display, a relatively large amplitude signal is output from the digital to analog converter. This large output signal turns on the...