# US 7,745,775 B2 · Testing of transimpedance amplifiers

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- Number: US 7,745,775 B2
- Document ID: US7745775B2
- Status: Granted
- Kind: B2
- Application number: 10/736,424
- Filed: 2003-12-15
- Published: 2005-06-16
- Granted: 2010-06-29
- Earliest claimed: 2003-12-15
- Assignees: International Business Machines Corporation
- Inventors: John Andrew Guckenberger; Young Hoon Kwark; Jeremy Daniel Schaub
- Web page: https://patentgrep.com/patent/US7745775B2

## CPC

- H04B 10/25: Arrangements specific to fibre transmission
- H04B: TRANSMISSION

## Abstract

Testing is performed on an amplifier wafer housing a transimpedance amplifier prior to packaging the transimpedance amplifier with an external photodetector, wherein the transimpedance amplifier includes a small, auxiliary, integrated silicon photodetector provided at the input of the transimpedance, in parallel with external photodetector attachment points. Totest the transimpedance amplifier, the transimpedance amplifier is stimulated by optically exciting the small auxiliary photodetector, wherein the small auxiliary photodetector is excited using short wavelength light, whereby advantages such as higher efficiency may be obtained. The testing method includes placing the amplifier wafer in a testing system, probing the power and ground connections on the amplifier wafer, illuminating the small auxiliary photodetector on the amplifier wafer, and detecting the output of the transimpedance amplifier housed on the amplifier wafer.

## Claims

### Claim 1

A transimpedance amplifier, comprising:
a substrate;
an amplifier circuit formed on said substrate;
a photodetector pad for connection to an external photodetector; and
an auxiliary photodetector formed on said substrate adjacent to said amplifier circuit.

### Claim 2 (depends on 1)

The transimpedance amplifier of claim 1, where said auxiliary photodetector does not significantly affect high speed performance of said transimpedance amplifier.

### Claim 3 (depends on 1)

The transimpedance amplifier of claim 1, wherein said substrate comprises at least one of silicon, silicon-on-insulator, gallium arsenide, indium gallium arsenide, and indium phosphide.

### Claim 4 (depends on 1)

The transimpedance amplifier of claim 1, wherein said amplifier circuit comprises at least one of metal oxide semiconductor, metal semiconductor, bipolar junction transistor, and heterojunction bipolar transistor.

### Claim 5 (depends on 1)

The transimpedance amplifier of claim 1, wherein said auxiliary photodetector comprises one of a P-N photodiode, a P-I-N photodiode, a metal-semiconductor-metal photodetector and an avalanche photodetector.

### Claim 6 (depends on 1)

The transimpedance amplifier of claim 1, wherein said auxiliary photodetector comprises a structure similar to that of a standard electro-static discharge diode.

### Claim 7 (depends on 1)

The transimpedance amplifier of claim 1, wherein said auxiliary photodetector is provided at an input of the transimpedance amplifier in parallel with attachment points to the external photodetector.

### Claim 8 (depends on 1)

The transimpedance amplifier of claim 1, wherein said auxiliary photodetector is provided to facilitate contact-less probing at input points of the transimpedance amplifier to test the transimpedance amplifier at wafer level.

### Claim 9 (depends on 1)

The transimpedance amplifier of claim 1, wherein said auxiliary photodetector is optically excited to test the transimpedance amplifier at wafer level.

### Claim 10 (depends on 9)

The transimpedance amplifier of claim 9, wherein said auxiliary photodetector is excited using short wavelength light.

### Claim 11 (depends on 9)

The transimpedance amplifier of claim 9, wherein said auxiliary photodetector is excited by illumination, and the transimpedance amplifier is tested by detecting an output of the transimpedance amplifier.

### Claim 12 (depends on 11)

The transimpedance amplifier of claim 11, where said output is detected by probing a supply voltage and detecting switching currents passing through a bias tee using a spectrum analyzer.

### Claim 13 (depends on 11)

The transimpedance amplifier of claim 11, where said output is detected using a high gain antenna and a sensitive narrow band receiver.

### Claim 14 (depends on 11)

The transimpedance amplifier of claim 11, where said output is detected using a high speed electrical probe by either direct contact or capacitive proximity coupling.