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Drive Method for Shorted Transmission Line

IP.com Disclosure Number: IPCOM000092927D
Original Publication Date: 1967-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Moore, RL: AUTHOR [+2]

Abstract

This circuit drives a shorted transmission line DL with two different voltage levels -V1 and -V2 to obtain a fast-pulse rise time. At the same time the power dissipation in transistor T1 controlling the current through DL is limited.

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Drive Method for Shorted Transmission Line

This circuit drives a shorted transmission line DL with two different voltage levels -V1 and -V2 to obtain a fast-pulse rise time. At the same time the power dissipation in transistor T1 controlling the current through DL is limited.

Initially, node A is biased at zero potential and diode D3, and transistors T1, T2, and T3 are biased nonconductive. However, when a signal pulse is applied to the input, T1 is turned on and current flows from -V1 through T1 and diode D1 to drive node A negative. As node A becomes negative, D3, T2, and T3 are driven conductive so that current can flow from -V2 through T2 and T1 into DL. Level -V2 is more negative than level -V1. Therefore, the current flow from -V2 back-biases D1 and causes the voltage at node A to go more negative. This initiates a current pulse which travels down DL. When this pulse is reflected back it causes the voltage at node A to return to zero. This turns T3 and T2 off so that -V2 is isolated from DL. D1 becomes forward biased so that DL is driven by -V1 during the flat top of the signal pulse. At the end of the signal pulse, T1 is turned off. D3, T2, and T3 remain inactive when T1 goes off.

Since -V1 is smaller than -V2, the initial use of the larger -V2 allows a rapid build-up of the current pulse. Switching to the smaller level -V1 prevents undesirably large voltages across T1 when the voltage across DL drops.

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