OPA859-Q1: What is the common mode input range of OPA859-Q when operating from single supply 3.3V

Hi Clemens,

Thank you very much.

Actually I am implementing discrete IrDA receiver.In my earlier board I used an IC from Analog devices.It is not automotive qualified.So decided to go with discrete implementation.Below is the block diagram of the IC. 

In the receiver section you can see that a trans-impedance amplifier + BPF + Comparator.

In my circuit I am using TIA + Comparator.I am using this opamp (OPA859-Q1) for my application.I use this opamp for TIA.

Why I used this high bandwidth opamp,the reason is given below.

The data rate of IrDA is 115.2 Kbps

Bandwidth≥3×Data Rate So for 115.2 kbps:Minimum Bandwidth≈3×115.2 kHz=345.6 kHz.
I considered 1 MHz (for margin and signal integrity).

The output of TIA is connected to a comparator and the comparator output will be connected to the microcontroller.

OPA859_Q_1_All_Curr_Hyst.TSC

I asked this discrete implementation question in many forums.Did not get any response.

Forum1:

Forum2:

May I know your thoughts.

Regards

For an IrDA receiver, a band-pass filter is important. There will be many other infrared sources, so you must filter out the 115.2 kbps signal (which uses a 3/16 pulse width). Also, AGC might be useful.

Thank you

In that case what will be the pass band frequency.

Also I found some other transceivers without BPF

www.vishay.com/.../tfdu4101.pdf

Sorry, I have no practical experience with this. You will have to do some research to find out how to handle the analog properties of the receiver.

I made small board with TIA and Comparator.Will experiment this week.I will update you

Hello Hari,

Here is some feedback on our end as well:

Current source: Analog current source from an IR LED? If so, then:

• Is input capacitance estimated to be around 1.3pF for intended reverse bias voltage from your schematic?
• What is estimated rise time, from pulse width min of 1.68us, I would assume around 100s of ns is needed, which would mean closed-loop bandwidth needed is 0.35/100ns = 35MHz or less.
• Can amplify to 1V, which for 3.8uA max current you would need around 250kOhms. This would set your GBW of amplifier requirement to around 5-6GHz. But, it is isn’t necessary to gain up that much since you are following this up with a filter + comparator. If you reduce to 100kOhms, it would put your GBW requirement to 1.5-2GHz around what the OPA859 can handle.
  • Recommended to set your DC bias to around 0.5V to 1V then make sure the max input current does not go above 1.7-1.9V. In that case RF value can change around depending on what you choose

  Useful Collateral: 

• TIA + Comp similar application circuit guide
• Reference Design Maximizing Transimpedance Bandwidth for LIDAR and Time-of-Flight Applications (shows similar application Diode+ TIA + comparator + microcontroller
• TLV7011: IR Receiver analog front end
  • TLV7011 has a useful datasheet section on this
• IR receiver type application
• Implementing IrDA With MSP430 MCUs

  Let us know how your experiment goes.

Thanks!
Sima 

Hi Sima,

Thank you very much.

This is my IR LED. Below is the IR LED Circuit.

This is my photodiode.

The input capacitance of the diode is taken from the datasheet for the particular reverse bias.This diode capacitance is small.

Regards

HARI

Dear Team,

I am happy to inform you tnat,We tested the circuit and it is working in lower data rates.

Regards

HARI

Hello Hari,

  Thank you for the update, I am glad it worked out!

Best Regards,
Sima