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Active Current Switch Driver

IP.com Disclosure Number: IPCOM000038327D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Chang, AY: AUTHOR [+3]

Abstract

A technique is described using a lateral PNP device to act as an active load across a fixed resistor in bipolar driver and array circuits for semiconductor applications. The new arrangement lowers the resistor's effective impedance and voltage drop with a resultant increase in the circuit's up-level and an improvement in its noise margin. The use of the PNP transistor with a push-pull driver is shown in Fig. 1. When all inputs are low in the push-pull driver, the NPN transistor TR is turned on by the Ics of the current source. The new PNP transistor Q1 will then be turned on to provide most of the base current which is required by the driving transistor Q5 .

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Active Current Switch Driver

A technique is described using a lateral PNP device to act as an active load across a fixed resistor in bipolar driver and array circuits for semiconductor applications. The new arrangement lowers the resistor's effective impedance and voltage drop with a resultant increase in the circuit's up-level and an improvement in its noise margin. The use of the PNP transistor with a push-pull driver is shown in Fig. 1. When all inputs are low in the push-pull driver, the NPN transistor TR is turned on by the Ics of the current source. The new PNP transistor Q1 will then be turned on to provide most of the base current which is required by the driving transistor Q5 . The current through the resistor element Rc is thereby reduced and the up-level of the emitter follower transistor Q5 is maintained at a higher level than in the conventional resistor case.

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The low output impedance of the PNP transistor in parallel with the resistor Rc reduces the effective base-driving resistance to the driver. This, in turn, will lower the driver impedance Zout, greatly enhancing the driving capability of the circuit. The arrangement with the word line decoder drive is shown in Fig. 2. In a similar fashion the new PNP transistor Q1 will function so that the reduction of current through the resistor Rc raises the up- level of the word line and allows for an increase of the Rc resistor value. Since the voltage swing of the word line is proportional...