THS4271 OPAMP 5V Single Supply and AC Coupled Configuration.

Eren AKKAYA

Other Parts Discussed in Thread: THS4271, THS4303

Hi,

I want to use THS4271 OPAMP with 5V Single Supply and AC Coupled.

The equivalent circuit of the source is signal source series with 8pF capacitor. I need 500kohm input resistance to reach my low frequency goal.

I am using THS4271 (SOIC) as buffer I selected Rf resistance value 200ohm, I am using split resistor technique for biasing and I chose Split resistor values R1 and R2 1Mohm because of to get 500kohm input resistance. Could you verify my circuit or suggest an alternative circuit to me?

Thanks,

over 13 years ago

0 Kris F over 13 years ago

TI__Genius 17905 points

Eren,

I believe this is related to our other conversation thread discussing your antenna amplifier (http://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/p/108306/382464.aspx#382464). I will close this thread so we will continue discussing on the other thread.

To answer the question, 500kohm effective resistance at the IN+ pin could cause the IN+ voltage to saturate and violate the input common mode range due to the high input bias current of 18 uA. You could run into the same problem you were facing with the THS4303 (other post).

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THS4271 OPAMP 5V Single Supply and AC Coupled Configuration.