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ADA4530-1 and LTC6079 with single supply in transimpedance application

Hello,

I am kindly asking advice on the following matter:

We are considering to use the AD4530-1 and the LTC6079 in an TIA configuration to condition

the photocurrent of a photodiode in a very low light application.

Since the circuit design will be single supply the following question arises:

Typically in single supply TIA circuits the opamp is biased on the positive input to move the signal

level away from the negative rail. The data sheet of the ADA4530-1 states that on page 31

"its input voltage range includes the lower supply rail and has a rail-to-rail output" .

Likewise the datasheet of the LTC6079 states on page 9

"The input stage of LTC6078/LTC6079 combines both PMOS and NMOS differential pairs,

extending its input common mode voltage range to both positive and negative supply voltages"

Now, does this mean both opamps can be operated in an TIA configuration to condition very low

currents without biasing the positive opamp terminal, but connecting it to GND?

Any advice is much appreciated!

Thank you very much
Peter

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  • Hi Peter,

    On the input side you can safely assume that the lower rail (V-) is included in the voltage range for both devices (LTC6079 includes both rails as the input voltage range). However, you'll have to consider that outputs are going to be mV's away from the rail, as shown under "output voltage" in both datasheets. Heavier output loading makes this voltage headroom larger.

    f you're ok with that, then you don't need to bias the input as you've described.

    Hope this answers your question.

    Regards,

    Hooman

  • Hi Hooman,

    thank you very much for the quick confirmation and the additional information regarding the output voltage!

    Cheers
    Peter

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