how to measure current in the TIA

[timedate]

For example, I have two feedback TIAs (with photodiode connected). I want choose the one with large input current signal, and the shunt down the other.

So, I have to measure the average current through the TIA, by means of measure the received optical power.

Does anybody know how to perform this function ? put a ADC connected to the TIA?

Thanks in advance.

 

[erikl]

Most simulators can measure the current through any component. If not, you could insert a 0Ω-resistor or a 0V-vdc which by default measure and show the current through them.

 

[D.A.(Tony)Stewart]

You could use a differential output TIA and compare outputs with a differential comparator and suppress the output not used for monitoring, but used going for the stronger signal with a combiner or Mux circuit..

https://www.analog.com/media/en/technical-documentation/data-sheets/AD8015.pdf

 

[timedate]

Thanks, but I mean the real circuit, not the simulation. Any hints?

 

[KlausST]

Hi,

you want to know the current through the diode?

It is output_voltage / feedback_resistor.
The feedback resistor should be known, the output voltage too, so it is simple math.

Or I misunderstood....?

Klaus

 

[D.A.(Tony)Stewart]

Thanks, but I mean the real circuit, not the simulation. Any hints?

I'm assuming you already have 2 TIA's and 2 PD's with 2 outputs

Are you familiar with an Analog Switch and comparator to select the higher output?

 

[crutschow]

Below is the LTspice simulation of a simple two op amp Analog Max. Value circuit, which should have a smaller output glitch when the output goes from one input to the other as compared to a comparator/analog switch circuit.
It's output is the maximum of the two inputs.

What is the maximum frequency of the inputs?