High Speed Amplifier suitable as a buffer

Morteza Kayyalha

Other Parts Discussed in Thread: INA111, THS3202, THS4271

Hello,

I have been using INA111 for the following circuit (3-omega measurement set-up) and it works perfectly fine up to 100KHz. However I need to push the fundamental frequency up to a few MHz and I couldn't find any good instrumentation amplifier for this matter! Does anyone have any suggestion of what to use? Please note that the swing is also very important and that's probably one reason that I cannot use INA111 above 200-300KHz.

Thanks,

Morteza

over 11 years ago

0 Hooman Hashemi over 11 years ago

TI__Mastermind 22825 points

Hello Morteza,

I cannot find an integrated instrumentation solution with much higher slew rate and bandwidth than the INA111. Here is a discrete possibility for your consideration:

Use two CMOS / JFET buffer Op Amps on the front and follow them with a high speed difference amplifier (4 matched resistors and an Op Amp with good high frequency CMRR).

Sorry but that's the closest thing I could conjure up.

Regards,

Hooman

0 Morteza Kayyalha over 11 years ago in reply to Hooman Hashemi

Prodigy 20 points

Hooman,

Thanks for your response! I was thinking of using something along the line of THS4271 or THS3202! Do you think they will do or do you have any suggestions?

Thank you,

Morteza

0 Hooman Hashemi over 11 years ago in reply to Morteza Kayyalha

TI__Mastermind 22825 points

Hi Morteza,

For your 2nd stage, I'd use a voltage feedback device (like the THS4271) and not the THS3202 (current feedback) because of more flexibility in input voltage range and the value of external resistors. You actually have a lot of choices for this amplifier and the next level of optimization is to choose the highest CMRR device (if your input CM has large variation and you are sensitive to that). Here is the prametric table if you like to fine-tune it:

http://www.ti.com/lsds/ti/amplifiers-linear/high-speed-amplifier-greater-than-equal-50MHz-products.page#p89=Voltage Feedback&p512=200;3000&p22typ=100;10500&p511=1;5

Regards,

Hooman

Amplifiers

Amplifiers forum

High Speed Amplifier suitable as a buffer