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Crystal Driver

IP.com Disclosure Number: IPCOM000083214D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Phillips, DW: AUTHOR [+4]

Abstract

This crystal driver solves the problem of providing a regulated 40 volt square-wave drive from a voltage differential of 32.4 volts, with a controlled rise and fall time to the crystal used in an ink jet printer. The circuit produces a square-wave output whose magnitude is greater than that of the biasing supplies, without the use of a step-up transformer.

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Crystal Driver

This crystal driver solves the problem of providing a regulated 40 volt square-wave drive from a voltage differential of 32.4 volts, with a controlled rise and fall time to the crystal used in an ink jet printer. The circuit produces a square-wave output whose magnitude is greater than that of the biasing supplies, without the use of a step-up transformer.

This drive uses two biasing voltages, +24 volts and -12 volts, and can provide a 45 volts peak-to-peak square-wave drive to a capacitive load.

The drive consists of five basic components, as shown in Fig. 1. Voltage regulator 1 is used to regulate the +24 volt supply, with respect to the -12 volt supply down to the voltage required to produce the desired output swing. "Bootstrapping" capacitor 2 is used to increase the peak-to-peak swing capability of the output, to a value of almost double the V1 to -12 volt voltage differential.

Buffer stage 3 helps prevent the bootstrapping capacitor from bleeding off, which would cause the square wave to droop while at its uplevel. Switching circuit 4 switches the output between its positive and negative levels. A logical square-wave input drives this stage. Output register 5 is used in conjunction with the capacitance of the load to set the rise and fall time of the square-wave output.

The details of the circuit are in Fig. 2. The voltage regulation is accomplished by the 723 block, transistor T1, and resistors R6 and R8. Potentiometer P1 is used to adjust the output to the desired voltage swing. The bootstrapping capacitor is C3. This capacitor is charged during the downlevel of the output. Its charge path is through diodes D1 and D2, resistor R1, diode D3 and transist...