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Esd-Protected TTL Receiver for Fet Products

IP.com Disclosure Number: IPCOM000047533D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Chang, HC: AUTHOR

Abstract

In transistor-transistor-logic (TTL) receiver circuits electrostatic discharge (ESD) protection is low and a sudden increase in voltage on the input of the circuit can cause the voltage across the gate of the input transistor to increase to levels sufficient to cause the gate oxide to break down and destroy the device. In the past it was proposed to insert a series resistor at the input of the circuit to attempt to mitigate this electrostatic discharge problem. However, such a series resistor causes an unwanted voltage drop at the input. By modifying the circuit, as shown in the figure, the electrostatic discharge protection of the circuit can be significantly increased.

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Esd-Protected TTL Receiver for Fet Products

In transistor-transistor-logic (TTL) receiver circuits electrostatic discharge (ESD) protection is low and a sudden increase in voltage on the input of the circuit can cause the voltage across the gate of the input transistor to increase to levels sufficient to cause the gate oxide to break down and destroy the device. In the past it was proposed to insert a series resistor at the input of the circuit to attempt to mitigate this electrostatic discharge problem. However, such a series resistor causes an unwanted voltage drop at the input. By modifying the circuit, as shown in the figure, the electrostatic discharge protection of the circuit can be significantly increased. In the circuit as shown, the input transistor 10 has its source coupled to the input and its drain coupled to the output and through a load transistor 11 to a voltage source 12. Coupled between the input and the chip substrate or ground is a protect device 13. This protect diode is in parallel with serially arranged capacitor C and a resistor R. The gate of the input transistor 10 is coupled to the junction between the capacitor C and the resistor R. The introduction of this resistor R into the circuit improves electrostatic discharge protection significantly. From the electrostatic discharge point of view the resistor R is as good as an input series resistor since it increases the time constant of the voltage across the gate capacitor C to allow the pr...