Amplifier configuration with noise reduction for a photodiode

1. A photodiode amplifier comprising: an amplifier having an amplifier inverting input, an amplifier non-inverting input, and an amplifier output;

a photodiode having a photodiode anode electrically connected with the amplifier inverting input and a photodiode cathode electrically connected with the amplifier non-inverting input;

a fixed voltage reference electrically connected with the photodiode cathode and the amplifier non-inverting input via a low pass filter;

a gain resistor coupling the amplifier inverting input with the amplifier output wherein a value of the gain resistance is at least doubled by multiplying at least twice a reference voltage and dividing it by a diode current, which establishes a voltage gain which is substantially equal to a low limit of an amplification of the amplifier; and

an analog to digital converter coupled to the amplifier output noise floor effects of the analog to digital converter accounted for via measuring a noise floor of the analog to digital converter by shorting inputs of the analog to digital converter.

2. The photodiode of claim 1 , wherein the fixed voltage reference is directly electrically connected to the low pass filter and the low pass filter is directly electrically connected to the photodiode cathode.

3. The photodiode of claim 1 , wherein the fixed voltage reference with the low pass filter is set substantially below a noise bandwidth of the photodiode amplifier.

4. The photodiode of claim 1 , wherein a voltage of the fixed voltage reference is selected to bias the photodiode amplifier such that there is increase in a usable output of the photodiode amplifier.

5. The photodiode of claim 1 , wherein the photodiode anode electrically connected with the amplifier inverting input forms an electrometer.

6. The photodiode of claim 1 , further comprising: a second stage amplification, the analog to digital converter coupled to an output of the second stage amplification, the second stage amplification coupled to an output of the photodiode amplifier.

7. The photodiode of claim 1 , further comprising: a low noise gain reduction circuit coupled to an output of the photodiode amplifier.

8. The photodiode of claim 1 , further comprising: an alternative feedback resistor coupled in parallel with the gain resistor.

9. The photodiode of claim 2 , wherein the low pass filter is outside of a signal bandwidth of the photodiode amplifier.

10. The photodiode of claim 5 , wherein an increase in an electrometer gain increases a useable signal range of the photodiode amplifier without substantially increasing the signal to noise ratio within a circuit.

11. The photo diode of claim 5 , wherein performance of the electrometer is increased by increasing an electrometer gain.

12. The photodiode of claim 5 , wherein the gain resistor is selected based upon a maximum available output signal range.

13. A method of amplifying a photodiode output, comprising the steps of:

supplying an output of a photodiode anode directly to an amplifier inverting input; supplying an output of a fixed voltage reference with a low pass filter to a photodiode cathode and an amplifier non-inverting input;

directing an amplifier output through a feedback gain resistance wherein a value of the resistance is at least doubled by multiplying at least twice a reference voltage and dividing it by a diode current, which establishes a voltage gain which is substantially equal to a low limit of an amplification; and

directing the amplifier output to an analog to digital converter, noise floor effects of the analog to digital converter accounted for via measuring a noise floor of the analog to digital converter by shorting inputs of the analog to digital converter.

14. The method of claim 13 , wherein a voltage supplied by the fixed voltage reference with the low pass filter is set substantially below a noise bandwidth of a photodiode amplifier.

15. The method of claim 13 , further comprising: selecting a voltage of the fixed voltage reference to bias a photodiode amplifier.

16. The method of claim 13 , wherein the photodiode anode is connected directly to the amplifier inverting input to form an electrometer.

17. The method of claim 13 , further comprising: supplying the output of the amplifier to a second stage amplification, the second stage amplification coupled to the analog to digital converter.

18. The method of claim 13 , further comprising: directing the amplifier output through an alternative feedback gain resistance to the amplifier inverting input.

19. A photodiode amplifier comprising:

an amplifier having an amplifier inverting input, an amplifier non-inverting input, and an amplifier output;

a photodiode having a photodiode anode electrically connected with the amplifier inverting input and a photodiode cathode electrically connected with the amplifier non-inverting input; a gain resistor coupling the amplifier inverting input with the amplifier output wherein a value of a gain resistance is at least doubled by multiplying at least twice a reference voltage and dividing it by a current of the photodiode, which establishes a voltage gain which is substantially equal to a low limit of an amplification;

a fixed voltage reference isolated from a amplifier power and electrically connected with the photodiode cathode and an amplifier non-inverting output;

a low pass filter is electrically connected to the fixed voltage reference wherein the low pass filter is outside of a signal bandwidth of the photodiode amplifier; and

an analog to digital converter coupled to amplifier output, noise floor effects of the analog to digital converter accounted for via measuring a noise floor of the analog to digital converter by shorting inputs of the analog to digital converter.

20. The photodiode of claim 19 , wherein the photodiode anode is electrically connected with the amplifier inverting input to form an electrometer.

21. A method comprising:

directing an output of an amplifier through a feedback gain resistance wherein a value of the feedback gain resistance is at least doubled by multiplying at least twice a reference voltage and dividing it by a diode current, which establishes a voltage gain which is substantially equal to a low limit of an amplification of the amplifier, an output of a photodiode anode supplied directly to an inverting input of the amplifier, an output of a fixed voltage reference with a low pass filter supplied to a photodiode cathode and a non-inverting input of the amplifier, the output of the amplifier supplied to a second stage amplification, the second stage amplification coupled to an analog to digital converter, noise floor effects of the analog to digital converter accounted for via a measurement a noise floor of the analog to digital converter, the noise floor measured by shorting inputs of the analog to digital converter.