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Browse Prior Art Database

Sign and Magnitude Current Driver

IP.com Disclosure Number: IPCOM000084013D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Brinson, AN: AUTHOR

Abstract

The circuit in Fig. 2 provides a load current waveform 1 in Fig. 1 in response to an input voltage or current signal waveform having a positive or negative peak of 0, as shown by waveforms 2 and 4, respectively, with a sign change at the peak of the input signal waveform as shown by sign waveform 3.

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Sign and Magnitude Current Driver

The circuit in Fig. 2 provides a load current waveform 1 in Fig. 1 in response to an input voltage or current signal waveform having a positive or negative peak of 0, as shown by waveforms 2 and 4, respectively, with a sign change at the peak of the input signal waveform as shown by sign waveform 3.

In Fig. 2, switches 13, 14, 16, and 17 are ganged together and are positioned as shown in response to a positive SIGN signal. A positive SIGN causes the wipers of each of the switches to be reversed from the configuration shown in Fig. 2. With a positive SIGN signal operational amplifier 11, Darlington transistor pair 18, 19, and resistor R12 form a negative feedback loop which maintains the inverting (minus) input of amplifier 11 at ground potential.

Similarly, operational amplifier 12 and resistor R22 also form a control loop which maintains the inverting input of amplifier 12 at ground potential. In the absence of any applied voltage signal at input terminal 10 or of any applied current signal at node C, current IA = 0 and the voltage VA at node A is maintained at ground potential.

Likewise, in the absence of any applied voltage signal at input terminal 20 and of any applied current signal at node D, current IB = 0 and the voltage VD at node D is maintained at ground potential. If a negative voltage signal is applied at terminal 10 or a current signal is drawn from node C or a combination of both occurs, resulting in IA being less than or equal to 0, then the voltage at node A becomes: VA = -IA(R12).

Similarly, if a positive voltage signal...