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Record Current Driver for Battery Operated Recorder

IP.com Disclosure Number: IPCOM000085395D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Higginbotham, AF: AUTHOR [+2]

Abstract

A record winding is driven by current proportional to input voltages which are summed and converted. The inputs which are summed are the record audio signal 1 from the preamplifier, the bias signal 3 from the bias-erase oscillator, and the index tone signal 2 from the tone attenuator.

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Record Current Driver for Battery Operated Recorder

A record winding is driven by current proportional to input voltages which are summed and converted. The inputs which are summed are the record audio signal 1 from the preamplifier, the bias signal 3 from the bias-erase oscillator, and the index tone signal 2 from the tone attenuator.

Operational amplifier AR1 is used both as a voltage-to-current converter and a summing amplifier. Transistor Q1 and its associated components resistors R7, R8, R9 and R11 function as a driver stage to supply the necessary signal current to record winding L1. Resistor R7 allows the output of amplifier AR1 to saturate to the downlevel without drawing excessive base current through transistor Q1. Resistor R8 insures that Q1 will turn off. Resistor R9 limits the gain of the driver stage to insure overall stability. Resistor R11 sinks current from winding L1 to ground during the positive half cycle of the output signal.

The bias level for the collector of transistor Q1 is approximately Vccl. When power is applied to the circuit, the inverting input of amplifier AR1 is driven positive with respect to the noninverting input; causing the output to saturate to the downlevel. This causes transistor Q1 to turn on; charging capacitor C3 through winding L1 and resistors 4, R5, and R10. When capacitor C3 charges to Vccl, the circuit stabilizes. Vccl is typically 1/2 Vcc3.

The combination of resistor R6 and capacitor C4 roll off the high-frequenc...