OPA838: Transimpedance amplifier with BPW34 (1us pulse width)

Simon Hackenberg

Part Number: OPA838
Other Parts Discussed in Thread: TINA-TI

Tool/software:

HI,

I am implementing a transimpedance amplifier based on the OPA838.

I am using a BPW34 and would like to detect and evaluate a signal of 1MHz. The approximate current flowing varies between 200nA and 80uA. A high-pass filter and a second amplifier stage will be installed. I came across the OPA838 and had a circuit suggested to me using the Photodiode Circuit Design Tool. I then rebuilt and simulated it with Tina. Unfortunately, the circuit does not work as desired and I am not sure why this is the case. The IG1 signal is at the moment for test purposes simply a square wave of 5uA with an offset of 5uA, so this should provide a square wave of 0-10uA with a frequency of 1MHz.

The bodeplot does look okey i think.

Does anyone know what I am doing wrong or what the problem could be?

Kind Regards

5 months ago

0 Aditya Gosavi 5 months ago

TI__Intellectual 2065 points

Hi Simon,

Thank you using the tool and providing the feedback.

Are you specifically asking why the the transient curve is behaving like that from 0 to 2us?

Can you please share your tina schematic, so that we can analyse it.

Regards,

Aditya

0 Simon Hackenberg 5 months ago in reply to Aditya Gosavi

Prodigy 10 points

Hi Aditya,

I think the circuit is not working properly.

Yes, exactly between 0-2us, I find it strange behavior.
If I set the supply voltage to 3.3V and GND as in the tool and I set the VBias to -3.3V as suggested in the tool, I get an error message.
If I change the supply voltage and lower the input current, the output no longer follows the 1MHz signal. (In the tool I have specified a range of 80uA-200nA)

I am aware that I am only allowed to feed the OPA838 with +-2.5V, I will change this if necessary.

1MHz_TIA.TSC

Regards,

Simon

0 Aditya Gosavi 5 months ago in reply to Simon Hackenberg

TI__Intellectual 2065 points

Hi Simon,

Thank you for providing all the details, I will look into it and get back to you.

Regards,
Aditya

0 Aditya Gosavi 4 months ago in reply to Aditya Gosavi

TI__Intellectual 2065 points

Hi Simon,

I wired up your circuit and I am not seeing any weird behaviour which is mentioned above. Please take a look at the screenshot below, I have also attached the TINA-TI schematic below. Let me know if I am missing something here.

1MHz_TIA_aditya.TSC

Regards,
Aditya Gosavi

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OPA838: Transimpedance amplifier with BPW34 (1us pulse width)