CONTROLLER FOR A PHOTOSENSOR

1 . A method of controlling a voltage driving a semiconductor photosensor within precise limits so as not to result in breakdown of the photosensor, said method comprising:

applying the drive voltage to the photosensor, the drive voltage being produced as an output voltage of a voltage converter as follows:

converting an input voltage to an output voltage via said voltage converter;

filtering said output voltage of said voltage converter via circuitry that includes a capacitance, wherein said capacitance is much less than a capacitance sufficient to maintain the photosensor voltage with said precise limits; and

applying the filtered output voltage at least as a portion of the input voltage of said voltage converter.

2 . The method of claim 1 , wherein filtering said output voltage is performed with said capacitance being less than 1 microfarad.

3 . The method of claim 1 , further comprising varying the drive voltage based at least in part on temperature changes of the photosensor.

4 . The method of claim 1 , further comprising driving the photosensor near the breakdown of the photosensor.

5 . The method of claim 1 , wherein the photosensor comprises a PIN photodiode.

6 . The method of claim 1 , wherein the photosensor comprises an avalanche photodiode (APD).

7 . The method of claim 1 , wherein the voltage converter comprises a DC-DC converter.

8 . An apparatus comprising:

a semiconductor photosensor including at least a control port;

a voltage converter having an output capacitor and an output port, said voltage converter to drive an output voltage within precise limits so as not to result in a breakdown of the photosensor, wherein the output capacitor by itself is not sufficient to maintain the output voltage within the precise limits; and

voltage converter feedback circuitry to receive a portion of said output voltage.

9 . The apparatus of claim 8 further comprising:

an RC filter coupled to said voltage converter feedback circuitry, wherein the capacitance of said RC filter is much less than a capacitance of the output capacitor.

10 . The apparatus of claim 9 , wherein the photosensor, voltage converter, feedback circuitry, output capacitor, and RC filter are incorporated in a single module.

11 . The apparatus of claim 10 , wherein said single module comprises a transceiver.

12 . The apparatus of claim 8 , wherein said voltage converter is incorporated in a low-profile 2 mm×2 mm integrated circuit module.

13 . The apparatus of claim 8 , wherein said output capacitor has a value less than 1 micro farad.

14 . The apparatus of claim 8 , wherein said precise limits include a limitation on a ripple voltage less than or equal to 0.3% of the control voltage.

15 . The apparatus of claim 8 , wherein said voltage converter to vary the output voltage at least partly based on temperature changes of the photosensor.

16 . The apparatus of claim 8 , wherein the photosensor comprises a PIN photodiode.

17 . The apparatus of claim 8 , wherein the photosensor comprises an avalanche photodiode (APD).

18 . The apparatus of claim 11 , wherein said transceiver comprises an SFP or an XFP module.

19 . The apparatus of claim 18 , wherein said SFP or XFP module comprises a hot pluggable, small footprint, serial-to-serial, data-agnostic, multirate optical transceiver.

20 . The apparatus of claim 8 , wherein the voltage converter comprises a DC-DC converter.

21 . A device comprising:

a circuit to drive an avalanche photodiode (APD) at a voltage less than a breakdown voltage and within precise limits by controlling a bias voltage to be applied to said APD, wherein said circuit includes:

a DC-DC converter including an input port and an output port to produce an output voltage;

a feedback loop to couple the input port to the output port and to scale said output voltage by a factor; and

a low-pass RC filter coupled to said output port, wherein the capacitance of the RC filter is much less than a capacitance sufficient to maintain said bias voltage with said precise limits.

22 . The device of claim 21 , wherein said circuit, APD, DC-DC converter, and the RC filter are incorporated in a single module.

23 . The device of claim 22 , wherein said single module comprises a transceiver.

24 . The device of claim 21 , wherein said DC-DC converter is incorporated in a low-profile 2 mm×2 mm integrated circuit module.

25 . The device of claim 21 , wherein the RC filter comprises a capacitor having a value less than 1 microfarad.