Browse Prior Art Database

Lower Barrier SBD Pull Down Driver Current Switch

IP.com Disclosure Number: IPCOM000088646D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Chang, AW: AUTHOR

Abstract

Fig. 1 shows a schematic of an invented current switch circuit with a Schottky barrier diode (SBD) coupling to the output emitter follower transistor. This compares to the Fig. 2 conventional current switch with emitter follower and load resistor.

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Lower Barrier SBD Pull Down Driver Current Switch

Fig. 1 shows a schematic of an invented current switch circuit with a Schottky barrier diode (SBD) coupling to the output emitter follower transistor. This compares to the Fig. 2 conventional current switch with emitter follower and load resistor.

The operation of Fig. 1 is as follows: When V 1N is at its high voltage level, point B will rise to VP and V02 will accordingly rise to drive the base(s) of the following stage(s). Since the B node is more positive than V02, diode D2 is reverse-biased at a VBE drop of 8 volts. When V IN is at the low voltage level, T2 will conduct. The current is determined by RE, and diode D2 will act like a clamp to the voltage level of one SBD (0.25 V at 1 mu amp for T1 with diode) drop above node B. This clamping action will effectively discharge all the capacitive charges on the base bus line. No DC load current is consumed at either voltage level of node V02 except for reasonable base currents at up level. Nodes A and V01 operate in a similar manner except that they are out of phase with the V IN.

An SBD can be integrated into the collectors of the transistor(s), T1 or T2 respectively.

To further improve the down switching time at the output(s), (VO1, V02), an additional clamping TREE of active devices can be designed (Fig. 3). A high barrier SBD (DH), such as a PtSi diode, plus the transistor diodes D3, D4 give a voltage source of 1.2 volts below VP. This is ideal to define a clam...