Browse Prior Art Database

Diode Transistor Buffer

IP.com Disclosure Number: IPCOM000086307D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Chang, HC: AUTHOR

Abstract

A diode transistor logic buffer is described which employs a base discharge diode to enhance the turn off time of the circuit and allow a reduction in the power dissipation thereof by removing a base-to-emitter resistor.

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Diode Transistor Buffer

A diode transistor logic buffer is described which employs a base discharge diode to enhance the turn off time of the circuit and allow a reduction in the power dissipation thereof by removing a base-to-emitter resistor.

The circuit shown in the figure without the diode DX is a standard diode transistor logic buffer driver. It consists of transistors T1, T2 and T3, the diodes D1, D2 and the resistors R1, R2, R3, R4 and RX. The resistor R3 is a low-value resistor for driving heavy loads. By disconnecting the optional connection 1, the device becomes a current sink and can interface off the semiconductor chip with large loads. The resistors RX and R4 are used to insure a quick discharge of the base node of the transistor T2 and the transistor T3, respectively.

The weakness of the prior art circuit is that the resistor RX steals charge from the base of the transistor T2 when the driver is in its on state, reducing its effectiveness. Increasing the resistance value of the resistor RX will help turn on times, but will slow turn off times for the circuit.

The improvement in the prior art buffer circuit described herein, is to use the base discharge diode DX in place of the resistor RX to drain charge from the base of the transistor T2 when the transistor T2 is turning off. Diode DX supplies a discharge path for the turn off of transistor T2, but will not steal charge when it is desired to turn the transistor T2 on. In addition, by removing the r...