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Constant Voltage, Current Sensing Circuit

IP.com Disclosure Number: IPCOM000052526D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Marcello, V: AUTHOR [+4]

Abstract

The circuit shown in Fig. 1 provides for the sensing of data stored in a selected cell of a Harper cell array matrix with improved performance and circuit stability over a typical prior-art scheme, as illustrated in Fig. 2. The proposed circuit represents basically a cascode current sensing amplifier with only one circuit being required to drive each data output circuit.

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Constant Voltage, Current Sensing Circuit

The circuit shown in Fig. 1 provides for the sensing of data stored in a selected cell of a Harper cell array matrix with improved performance and circuit stability over a typical prior-art scheme, as illustrated in Fig. 2. The proposed circuit represents basically a cascode current sensing amplifier with only one circuit being required to drive each data output circuit.

Fig. 2 shows a partial schematic voltage sensing circuit which is typical for prior-art schemes. Nodes SL and SR are switched by the sense current IR to provide a differential sense to the output amplifier. However, this circuit operation is relatively slow, since a large capacitive load, due to the collector dot function, is seen at nodes SL and SR. As array densities increase, this type of circuit becomes even slower due to the larger number of collector dots required. Therefore, a current sensing circuit is desirable to achieve better performance.

In the proposed circuit shown in Fig. 1, the read current IR is sensed either by T4 or T7, allowing its respective collector to be switched to a zero state. The voltages at the collectors of T4 and T7 are translated to nodes SL and SR which drive the output amplifiers. The transitions at SL and SR are relatively fast since capacitive loading is maintained at minimum.

Nodes 1 and 2 (collector -16-way- dot) are also maintained constant by biasing the bases of T4 and T7 at a constant voltage and maintaining a mi...