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Low Power Current Switch Emitter Follower

IP.com Disclosure Number: IPCOM000089726D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Blumberg, RJ: AUTHOR [+2]

Abstract

The circuit shown in Fig. 1 discloses a low power, low voltage, current switch emitter follower circuit. It has a subnanosecond switching speed. The circuit is suitable for on chip usage where density is an important factor. The power dissipation for a 1 ma current switch and a 1 ma emitter follower node is nominally 4.5 mwatts. The circuit is designed to operate with an external 3-volt supply for VEE, a 1.5-volt supply for the emitter follower termination, and ground for VCC. The constant current source bias VX and the reference potential VR are generated by an on-chip bias circuit.

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Low Power Current Switch Emitter Follower

The circuit shown in Fig. 1 discloses a low power, low voltage, current switch emitter follower circuit. It has a subnanosecond switching speed. The circuit is suitable for on chip usage where density is an important factor. The power dissipation for a 1 ma current switch and a 1 ma emitter follower node is nominally 4.5 mwatts. The circuit is designed to operate with an external 3-volt supply for VEE, a 1.5-volt supply for the emitter follower termination, and ground for VCC. The constant current source bias VX and the reference potential VR are generated by an on-chip bias circuit.

As seen in Fig. 1, the collector circuits of both the in-phase side and the out- of-phase side of the current switch share a resistor R1. This resistor serves to inhibit the up-level of either phase. The current switch current demanded by the constant current source always flows through this resistor independent of which side is conducting. The emitter follower resistors are returned to 1.5 volts, which results in the emitter followers being completely shut off in the down-level state.

The decreased swing of 1.0 volt to 1.5 volts, as opposed to the conventional
0.8-volt swing, allows for an improved AC performance. This improvement is due to the wavefrom crossing the threshold of the circuit sooner because of the smaller signal swings. This swing of approximately 0.5 volt still maintains sufficient noise tolerance because these circuits only...