The Signal - All Comments

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: Taming the Oscillating Op Amp

Giorgio Minai — Tue, 11 Feb 2025 00:10:12 GMT

Hi Bruce, could you please post the link to the post that followed this one?

RE: Illuminating Photodiodes ;-)

shuai li — Sat, 08 Feb 2025 09:29:36 GMT

Hello Bruce

thanks for your sharing and i got a problem

why you say that "You can get some of the benefits of photoconductive mode simply by loading a photodiode with a low value resistor, say around 50 ohms. If the diode voltage does not exceed 20mV, or so, you do not significantly forward bias the diode and response is reasonably linear and fast. Sensitivity, however, is low."in your topic.

how to understand this word?

RE: Illuminating Photodiodes ;-)

shuai li — Sat, 08 Feb 2025 09:26:23 GMT

hello Bruce

thanks for your sharing and i got a problem

how to understand this word?

RE: Knowing Where to Tap

Paul Braineard — Sun, 07 Jul 2024 10:57:59 GMT

Thank you very much Bruce for the tremendous knowledge you have shared with us, hope this light continue to glow forever. God bless.

RE: Paralleling Op Amps—is it possible?

Gabriel Jonquieres — Tue, 30 Apr 2024 01:09:39 GMT

Hi,

Can I parallel 4x opamps 1 master 3 slaves in cascade each one another ? So I can drive 600ohms resistor in feedback of my shelf filter audio circuit with 22nF high grade duelund capacitor (no smaller value existing) and get the right RC value for the frequency I need.

I saw this rule in audio circuits of not going over 1/10 linear output current of the opamp in the feedback loop, this is why I need 4x opamps to meet this spec.

So Is it better to go for 1/5 linear output current and use only 2 opamps ?

RE: Difference Amplifiers—the need for well-matched resistors

James Kim — Thu, 26 Aug 2021 12:34:39 GMT

I just accessed the files Time Sobering placed in his profile, I had no problems at all downloading them. The fence installation Harris Ap Note looks quite good. Thanks Bruce.

RE: Breadboarding with Micro-Packages—Ouch!

James Kim — Thu, 26 Aug 2021 12:33:16 GMT

This is how I would do such a simulation to have an information about stability - So far I did that with OpAmp/MOSFET current sources. My experience is that many sources looked critical but stable, but in reality they were not stable... I had to apply a dumpster rental compensation and with much margin in the loop the simulation did a good job.

RE: SPICEing Op Amp Stability

James Kim — Thu, 26 Aug 2021 12:31:26 GMT

My suggestion for improving the stability and for the same frequency bandwidth of this circuit is shunting the R2 concrete contractor resistor with 27pF capacitor and don't use the input R3, C1 filter.

RE: Temperature Effects on Input Bias Current… plus a Random Quiz

Johny Kim — Wed, 25 Aug 2021 12:03:03 GMT

To be honest, less is known about the behavior below room temperature because the higher leakage at room temperature towing and above is the greater concern. It’s best not to place high confidence in behavior much below room temperature.

RE: Holiday Brain Teaser

Johny Kim — Wed, 25 Aug 2021 12:01:24 GMT

Nice resistor puzzle. I enjoyed doing this.

Cheers!

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RE: Brain Teaser—the solution

Johny Kim — Wed, 25 Aug 2021 11:59:24 GMT

Awesome! Such a great help for me since I am having a hard time solving a problem like this.

Cheers!

John Driveways

RE: Making Your Own Difference Amp—sometimes 1% resistors are good enough

Alex Scott — Wed, 25 Aug 2021 11:53:03 GMT

I was dinged on this concept during an interview. I only knew that it is beneficial to have a higher gain block in front of a bed bug control cascaded signal chain, but I did not know the technical reason why and I certainly did not know the math behind it. After the interview I scoured the web and now I know it as Frii's Formula.

RE: Slew Rate—the op amp speed limit

Alex Scott — Wed, 25 Aug 2021 11:52:03 GMT

Checked already! Thanks.

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RE: “I Need High Input Impedance!”

Alex Scott — Wed, 25 Aug 2021 11:49:28 GMT

I agree that flowing in certain sensors and chemical cells such as pH probes, it can polarize the electrodes, creating drywall repair error and even causing permanent damage. Input bias current will charge the capacitor of an integrator circuit, creating a ramping output with zero input.