# US 5,349,287 A · Low power comparator having a non-saturating current mirror load

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- Number: US 5,349,287 A
- Document ID: US5349287A
- Status: Granted
- Kind: A
- Application number: 07/958,380
- Filed: 1992-10-08
- Granted: 1994-09-20
- Earliest claimed: 1992-10-08
- Assignees: National Semiconductor Corporation
- Inventors: Perry S. Lorenz
- Web page: https://patentgrep.com/patent/US5349287A

## CPC

- G05F 3/26: Current mirrors
- G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

## Abstract

ECL to TTL converter circuits are shown having current mirror loads which produce the required differential to single-ended conversion. Saturation is avoided in the current mirror by connecting a resistor between the collector and base the output transistor.

## Claims

### Claim 1

An ECL to TTL converter employing a differential driver input responsive to ECL signals, said driver being coupled to current mirror load comprising:
an input transistor having its collector coupled to its base thereby to operate as a diode;
an output transistor having a collector and having its base coupled to said input transistor base;
a resistor connected between said output transistor collector and base whereby saturation is avoided in said output transistor; and
output buffer means coupled to said collector of said output transistor whereby TTL output signals are developed.

### Claim 2 (depends on 1)

The ECL to TTL converter of claim 1 wherein said differential driver comprises:
a pair of emitter follower transistors having their inputs driven differentially by said ECL signals; and
means for coupling the outputs of said pair of emitter follower transistors to said current mirror.

### Claim 3 (depends on 2)

The ECL to TTL converter of claim 2 wherein said pair of emitter follower transistors and said current mirror comprise NPN transistors.

### Claim 4 (depends on 1)

The ECL to TTL converter of claim 1 wherein said differential driver comprises:
first and second input transistors having their emitters coupled together and to a constant current element thereby producing differential operation; and
means for applying said ECL signals to the bases of said first and second transistors.

### Claim 5 (depends on 4)

The ECL to TTL converter of claim 4 wherein said first and second transistors are PNP transistors having their emitters connected to a constant current source and said current mirror transistors are NPN transistors.