Miniature low-noise photodiode system

• US 6,444,970 B1
• Filed: 06/24/1999
• Issued: 09/03/2002
• Est. Priority Date: 06/26/1998
• Status: Expired due to Term

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Scimed Life Systems Incorporated (Boston Scientific Corporation)
• Inventors: Barbato, Louis J.
• Primary Examiner(s): PYO, KEVIN K
• Application Number:
  US09/339,695
• Time in Patent Office: 1,167 Days
• Field of Search: 250/214.A, 250/214.LA, 250/214.R, 250/214.AG, 250/214.C, 250/226, 330/308, 330/59, 330/291, 356/416, 356/417, 356/419, 606/2, 606/14, 606/15
• US Class Current: 250/214.00A
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: H03F 3/087 with IC amplifier blocks H03F3/085 takes precedence

Abstract

A miniature low-noise photodiode amplifier system that minimizes offset and drift has the output of a photodiode connected to the non-inverting input of an operational amplifier. The operational amplifier has a split voltage supply and the output of the operational amplifier is transmitted to a rectifying diode. A second amplifier to increase the output of the operational amplifier is not required when this miniature low-noise photodiode amplifier system is employed.

Claims

1. An amplifier circuit, comprising:

an operational amplifier, including an inverting input, a non-inverting input, and an output;

a light-sensitive device comprising a first terminal and a second terminal, the first terminal in electrical communication with the non-inverting input of the operational amplifier and the second terminal connected to ground;

a feedback module in electrical communication with the output of the operational amplifier and the inverting input of the operational amplifier; and

a rectifier in electrical communication with the output of the operational amplifier.

2. The amplifier circuit of claim 1 wherein the rectifier comprises a rectifying diode.

3. The amplifier circuit of claim 1 further comprising a resistance in electrical communication with the inverting input of the operational amplifier.

4. The amplifier circuit of claim 1 further comprising a resistance in electrical communication with the rectifier.

5. The amplifier circuit of claim 1 wherein the feedback module includes a resistor.

6. The amplifier circuit of claim 5 wherein the feedback module further includes a capacitor.

7. The amplifier circuit of claim 1 wherein the light-sensitive device comprises a photodiode.

8. A spectroscopy probe, comprising:

an amplifier circuit comprising an operational amplifier, a feedback module and a rectifier;

the operational amplifier comprises an inverting input, a non-inverting input, and an output;

the feedback module is in electrical communication with the output of the operational amplifier and the inverting input of the operational amplifier; and

the rectifier is in electrical communication with the output of the operational amplifier;

a light source for illuminating tissue; and

a light-sensitive device comprising a first terminal and a second terminal, the first terminal in electrical communication with the non-inverting input of the operational amplifier and the second terminal connected to ground, wherein the light-sensitive device detects optical properties of the illuminated tissue.

9. The spectroscopy probe of claim 8 wherein the light source is internal to the spectroscopy probe.

10. The spectroscopy probe of claim 8 wherein the amplifier circuit comprises a plurality of operational amplifiers.

11. The spectroscopy probe of claim 8 further comprising a light filter disposed between the illuminated tissue and the light-sensitive device.

12. The spectroscopy probe of claim 11 further comprising a second light-sensitive device and a second light filter disposed between the illuminated tissue and the second light-sensitive device.

13. The spectroscopy probe of claim 12 wherein the first light filter passes through a first range of wavelengths of light and the second light filter passes through a second range of wavelengths of light.

14. A method for amplifying an output of a light-sensitive device comprising:

a) providing an amplifier circuit comprising the light-sensitive device, an operational amplifier, and a rectifier, wherein a non-inverting input of the operational amplifier is in electrical communication with a first terminal of the light-sensitive device and a second terminal of the light-sensitive device is connected to ground;

b) applying a first voltage to an inverting input of the operational amplifier;

c) detecting an optical signal through the light-sensitive device, wherein the light-sensitive device converts the optical signal to a second voltage;

d) applying the second voltage to the non-inverting input of the operational amplifier, wherein the first voltage and the second voltage have opposite polarity;

e) applying an output generated by the operational amplifier to the rectifier; and

f) transmitting the output having a polarity of the second voltage through the rectifier.

15. The method of claim 14 further comprising the step of stabilizing the output transmitted through the rectifier.

16. The method of claim 14 wherein step b comprises applying the first voltage from the output of the operational amplifier to the inverting input of the operational amplifier.

17. The method of claim 14 further comprising filtering noise in connection with the optical signal.