Instrumentation Amplifiers—avoiding a common pitfall

RE: Instrumentation Amplifiers—avoiding a common pitfall

Valentín Mariatti — Thu, 09 Oct 2025 20:49:30 GMT

Hey Bruce, i got a question

Im trying to do an instrumentation amplifier using OP07's, before the non inverting inputs i have buffers, wich where made using follower emitters. Does the emitter resistor provides the bias current needed.

Thanks in advance!

RE: Instrumentation Amplifiers—avoiding a common pitfall

Bruce Trump — Sun, 24 Mar 2013 21:07:09 GMT

Jim-- Posting an image to our forum can seem a bit tricky. You cannot paste an image directly into the browser-based editor. There are two ways: The "Insert Image" icon allows you to navigate to an image file (jpg, gif, etc) on your computer. Browse to find your image, click open and see the indicator show the file loading. Then press the red "Insert" button. You can attach a file of any type (pdf, etc.) using the "Insert File" icon. The procedure is similar. -- Bruce

RE: Instrumentation Amplifiers—avoiding a common pitfall

Jim Carlini — Sun, 24 Mar 2013 20:54:51 GMT

Hi Bruce,

I tried for some time to leave a picture of my schematic using numerous methods. However I don't believe I was successful. Is there a trick to it?

Jim

RE: Instrumentation Amplifiers—avoiding a common pitfall

Bruce Trump — Fri, 22 Mar 2013 19:52:22 GMT

Jim-- It's necessary to get into the details of your application to answer your question. I suggest that you post a question on our precision amplifiers E2E forum. The link is below figure 3 in this blog. Postings on the forum allow sharing of schematics which cannot be done in these comments. Be sure to provide details on your input signal, power supplies, etc. -- Bruce

RE: Instrumentation Amplifiers—avoiding a common pitfall

Jim Car — Fri, 22 Mar 2013 18:32:23 GMT

. Hi Bruce,

What a good way to bias this instrumentation amplifier circuit for single supple use (W/O a transformer).

Thank you,

Jim

RE: Instrumentation Amplifiers—avoiding a common pitfall

Bruce Trump — Fri, 14 Dec 2012 12:51:35 GMT

Abhijit-- Your question pertains to an op amp circuit and does not relate directly to this blog topic. An instrumentation amplifier does not have feedback from output to the inverting input. The op amp circuit I believe you are describing is a multiple-feedback high-pass filter. In this case the output of the op amp provides a bias current path for the inverting input. If you have further questions on this, I suggest that you submit to the precision amplifier forum and include a schematic.

RE: Instrumentation Amplifiers—avoiding a common pitfall

Abhijit Pethkar — Fri, 14 Dec 2012 10:14:57 GMT

Dear Bruce,

How do you explain for the High Pass Butterworth filter where a capacitor filter is placed at the input of the filter. Only one resistor is connected to the ground for the positive terminal where as the negative terminal has capacitors both at the input and output of the Op Amp.

Regards