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TIDA-01486: Available gain for the THS3095

Part Number: TIDA-01486
Other Parts Discussed in Thread: THS3095,

Hi,

I've read in the TIDA-01486 that you have adjusted the gain of the op amp on the board. You changed them from 10 to 2. You have adviced to look at recommended resistor values in the THS3095 datasheet. My question is:

There is recommended value for 1,2,5 & 10 gain , is it possible to use a gain in between the recommended values ?

Thank you,

Simon.

• Hello Simon,

Yes, other gains in between the recommended values can be used. With current feedback amplifiers, the feedback resistor of the device plays a large role in determining the amplifier's stability. I would suggest using the following method for determining the Rg & Rf values for a different gain:

A current feedback amplifier's feedback factor follows the following equation: "Rf + Ri*NG"

With Rf being the feedback resistor, Ri being the inverting input resistance and NG being the noise gain of the circuit. To follow the recommended resistances on table you can interpolate for the desired gain you would like. So for a gain of 3 for example, you will use the equation above for gains of 2 & 5 found in the table 4.

In this case: 1.21k + Ri*2 = 1k + Ri*5, solving for Ri we get Ri = 70 ohms.

Using Ri =70 to solve for our new gain: Rf + 70*3 = 1.21k + 70*2

Rf = 1.14k

So the recommended resistances for a non-inverting gain of 3 would be, RF = 1.14k & Rg = 570

You can find a more detailed discussion of this on this video:

https://training.ti.com/ti-precision-labs-op-amps-current-feedback-amplifiers-overview-and-compensation-techniques

Best,

Hasan Babiker

• Thank for this detail answer.

Simon.