Home    Bloggers    Blogs    Article Archives    Messages    About Us   
Tw  |  Fb  |  In  |  Rss
Dennis Feucht

Case Study: Medical Laser System; Part 2: Photodiode Amplifier

Dennis Feucht
Page 1 / 2 Next >
D Feucht
D Feucht
11/27/2017 3:42:35 PM
User Rank
Re: photodiode operation
Thanks for your comment on photodiode modes. Indeed, in zero-volts mode, there should be no effect from the PD capacitance, though it will need to be compensated in the feedback loop. I call the reverse-biased mode the "voltage mode" because there is a voltage across the diode. In the "current mode", with no voltage across the PD, it doesn't seem like much of a "voltage" mode. But these are just labels.

For the laser application, the revised (current?) mode worked better.

11/15/2017 11:53:34 AM
User Rank
photodiode operation
"uses the photodiode in the fast but noisy voltage mode." It's my experience that current-mode is the fastest operation.  With no voltage variation there's no loading by the diode's or circuit capacitance.  Gives better linearity also.

Seems like the first paragraph under "Mode" is describing current mode.  And, yes, this gives more dark current if the diode is reverse-biased.

In current mode bootstrapping can virtually eliminate the effects of diode capacitance.

More Blogs from Dennis Feucht
A seemingly simple circuit with only two components, an op-amp and a feedback resistor, is commonly used to convert a current to a voltage. This circuit is familiar as a photodetector or impedance-meter current-sense amplifier.
Oscilloscope triggering circuits can be adapted to other applications, as precision synchronizers. Both analog and digital ‘scope triggering has been enhanced by various auto-trigger schemes. This tutorial overview of ‘scope triggering circuits and schemes presents the basics of trigger generators and also some enhancements
Hard copy electronic catalogs: Be bold, go old, and succeed
In this part, we push forth to transfer functions in s and z of ADCs and DACs, then consider briefly how to design feedback loops that span the analog-digital boundary.
flash poll
educational resources
follow Planet Analog on Twitter
Planet Analog Twitter Feed
like us on facebook
our partners
Planet Analog
About Us     Contact Us     Help     Register     Twitter     Facebook     RSS