1
\$\begingroup\$

I am working with LTC6253-7 op amp which should have a bandwidth of 2 GHz but when I simulate the output for a follower and the output is being severely attenuated. Is there a technique that must be used to achieve unity gain? My signal is 500 MHz I am using to test this op amp. enter image description here

enter image description here

\$\endgroup\$
5
  • 1
    \$\begingroup\$ The LT part numbers ending with dashed numbers means the minimum gain for stability. If you need unity gain stable, I would try the AD8000 recommended to you in your previous question: analog.com/en/products/ad8000.html \$\endgroup\$
    – Ste Kulov
    Commented Jun 25 at 20:15
  • 1
    \$\begingroup\$ Also, I noticed you post many questions and never accept any answers. See this for more info: meta.stackexchange.com/a/5235 \$\endgroup\$
    – Ste Kulov
    Commented Jun 25 at 20:16
  • \$\begingroup\$ I should also note that most GHz range unity gain opamps will be "current feedback" instead of "voltage feedback". \$\endgroup\$
    – Ste Kulov
    Commented Jun 25 at 20:22
  • \$\begingroup\$ but you can use them the same way right? so i think its ok. \$\endgroup\$ Commented Jun 25 at 22:03
  • \$\begingroup\$ Ehhhh...mostly, but there are some differences. One important thing is that CFB opamps usually have a very limited input and output range, so you don't have much headroom operating from a single supply. Additionally, I think for your application (unity gain buffer) you need to be careful of the feedback resistor. See Figure 4 and the text above it in the following application note: ti.com/lit/pdf/sboa081 \$\endgroup\$
    – Ste Kulov
    Commented Jun 26 at 6:47

1 Answer 1

3
\$\begingroup\$

It's quite simple. You are using the device outside it's prescribed limits as stated in the data sheet: -

The device is stable for closed loop noise gains of 7 or higher

In other words, the minimum gain is not unity but 7. More info from the data sheet: -

Gain Bandwidth Product: 2 GHz
–3dB Frequency (AV = 7): 160 MHz

I am working with LTC6253-7 op amp which should have a bandwidth of 2 GHz

No, it has a gain-bandwidth-product of 2 GHz

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.