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Faster And Denser Bipolar Sense Amplifiers for BICMOS SRAMS

IP.com Disclosure Number: IPCOM000102497D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 97K

Publishing Venue

IBM

Related People

Hauviller, P: AUTHOR [+2]

Abstract

This disclosure relates to sense amplifiers using bipolar transistors for BICMOS SRAMs. The proposed sense amplifier (SA) includes improvements to standard 3-stage bipolar sense amplifiers which result in 1) decreasing the device count (and then the consumed area) and 2) increasing the speed with no increase in power consumption.

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Faster And Denser Bipolar Sense Amplifiers for BICMOS SRAMS

       This disclosure relates to sense amplifiers using bipolar
transistors for BICMOS SRAMs. The proposed sense amplifier (SA)
includes improvements to standard 3-stage bipolar sense amplifiers
which result in 1) decreasing the device count (and then the consumed
area) and 2) increasing the speed with no increase in power
consumption.

      The speed limit is due to the combination of a large amount of
capacitance at the dotted outputs of a group of sense amplifiers (see
Fig. 2) and the wiring resistance plus the input resistance of the
following stage which is of the common base (CB) amplifier type. This
capacitance consists of the collector-to-substrate capacitance (CCS)
and the collector-to-base capacitance (CCB) of output transistors T5
and T6 in Fig. 1 which shows the sense amplifier schematic.

      Nothing can be done to decrease the effect of CCS capacitance
except decreasing the number of the sense amplifier dotted outputs
(this will be explained in the next paragraph).

      However, the effect of the CCB capacitance can be reduced by
having the base voltage varying in the same manner as the collector
voltage. This is realized by decoupling the diode biasing network
(diodes D1, D2 in Fig. 2), actually creating 2 separate biasing
networks (diodes D1 to D4 in Fig. 2 with the same type of transistors
as those used in the common base stage).

      Wiring resistance, Rmb, is added in series with the biasing
networks in the same manner and amount as the wiring resistance Rms
when the circuit is laid out. When th...