OPA838: OPA838IDBV

derek murison

Part Number: OPA838
Other Parts Discussed in Thread: TINA-TI, , OPA836

Tool/software:

OPA838IDBV used with a 5V single supply. 5V confirmed at pin5 & 6. Vref is disconnected from any other circuitry.

A simple circuit here, but it doesn't work. 2.5V at the potential divider rises to 3.9V when the op-amp is populated. Vref = 3.9V. The white line on the body aligns with pin1 & 6. Found no reference to how to determine correct orientation using the body markings. Can't see why this doesn't work. Input range is restricted (not rail to rail) but an input of 2.5V should be ok. Baffled.

3 months ago

0 derek murison 3 months ago

Prodigy 30 points

Meant to add that it simulates fine in Tina-TI

0 derek murison 3 months ago in reply to derek murison

Prodigy 30 points

I did not clear GND & PSU planes under the input.

+1 Vikas Jeevannavar 3 months ago

TI__Expert 3005 points

Hi derek murison,

OPA838 is a decompensated amplifier which works with minimum gain of 6V/V. You can refer to 3 common questions when designing with high-speed amplifiers for more information on decompensated amplifier. You can use a P2P device OPA836 which works in a unity gain configuration. Based on your Iq, Noise, package and cap load drive requirements, you can choose appropriate amplifier from High-speed op amps (GBW ≥ 50 MHz) product selection | TI.com

Thanks
Vikas J

0 derek murison 3 months ago in reply to Vikas Jeevannavar

Prodigy 30 points

Vikas,

Thanks. I have ordered OPA836 which I am very familiar with. I am using OPA838 in the same design but with 10V/V gains. Wish Tina-TI was able to simulate the instability in the 1V/V configuration.

Regards

Derek

0 derek murison 3 months ago in reply to derek murison

Prodigy 30 points

Vikas,

OPA836 now fitted & working. Thanks.

Regards

Derek

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OPA838: OPA838IDBV