#opamp

[icgoodfind]

#optoelectronics #PS2805 #RENESAS #OPA189 #TI #texasinstruments #OPAMP #CTTF0505-1T #MORNSUN #power #chip #hardware #icgoodfind #Electronics platform: www.icgoodfind.com

[mesotokyo]

OPアンプを差し替えると動作が変わる回路

OPアンプは帰還型の回路で使うのが一般的なので、定格内の動作なら別のOPアンプに差し替えても動作は変わらないだろうと思ったら大間違いだぞという話です。

上の回路は、OPアンプを使ったバッファ回路です。入力は直流成分をコンデンサで除去するACカップリングになっていますが、出力はOPアンプの出力をそのまま（抵抗だけ入れて）出しています。後段に別の回路を組み込むような場合このような回路を使うことが多いかと思います。この回路では、OPアンプにJFETタイプのLT1057を使用しています（オーディオ系工作でよく使われるTL072と似たような特性なので、自分はLTSpiceでのシミュレーションでよく使っています）。シミュレーション結果を見ると、入力と出力はほぼ一致しています。

さて、回路構成は同じで、OPアンプだけを別のLT1813に変えてみたものが次の回路です。シミュレーション結果では、なんと出力に0.8Vほどのオフセット電圧が加わってしまっています！

この違いは、OPアンプの入力バイアス電流が原因で発生します。入力バイアス電流は、OPアンプの+/-それぞれの入力端子に流れ込む電流のことです（Analog Devicesによる解説資料）。データシートによると、LT1057の入力バイアス電流は標準で±7pA、最大で±75pAとされています。いっぽう、LT1813の入力バイアス電流は標準で-0.9μA、最大で±4μAとなっています（入力バイアス電流がマイナスということは、+/-それぞれの端子から電流が流れ出ることを意味しています）。

この回路では、+入力端子が1MΩの抵抗（R7）を介して接地されています。入力バイアス電流は直流なのでコンデンサ（C1）は通らず、すべてR7に流れます。入力バイアス電流が7pAの場合、これによって生じるGNDとの電位差は7μVと一般的には無視できるレベルですが、0.9μAの場合は0.9Vというかなり大きめの値になってしまいます。

このような回路構成の場合、入力バイアス電流によって発生した電圧が直接入力電圧に加算され、そのまま出力に出てきます。これは増幅率1のユニティゲイン回路ですが、たとえば非反転増幅回路の構成にした場合は入力バイアス電流によって発生した電圧も増幅されるため、より出力信号に加わるバイアス電圧は大きくなります。

入力バイアス電流の対策方法

今回のような回路では、入力端子に接続する抵抗の抵抗値を小さくすることで出力電圧に加わるバイアスを減らすことができます。たとえば、R7を100分の1の10kΩに変更すると、次のように出力と入力の差は小さくなります。

もちろん、入力バイアス電流が小さいOPアンプを選択するというのも（選択肢があるのであれば）良い解決方法でしょう。上記で紹介したAnalog Devicesの資料ではほかにもいくつかの対策方法が紹介されています。

入力バイアス電流の大きいOPアンプ

入力段にCMOSやJFETを使ったOPアンプは入力バイアス電流が小さく、バイポーラトランジスタを使ったOPアンプは入力バイアス電流が大きい傾向があります。たとえば、オーディオ用OPアンプとしてよく使われるNJM4580は入力段にバイポーラトランジスタを使っているため、入力バイアス電流が大きめで、データシートによると標準で100nA（0.1μA）、最大で500nA（0.5μA）です。TL072はJFETタイプで標準で20pA、最大で200pAなので、TL072を使った回路でOPアンプをNJM4580に差し替えると、回路によってはこの入力バイアス電流による影響を大きく受ける可能性があります。

[guitarbomb]

Ground Control UwU Virtual Pet Buffer - With OLED virtual pet

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[edisonsciencecorner]

I MADE A custom line sensor array for my line follower robot. It has 5 IR CHANNELS individual sensing adjustment LED indication @jlcpcb #linefollowerrobot #linefollower #ir #irsensor #irmodule #qtr #pololu #robotics #pcb #electronics #makers #lm358 #opamp #led https://www.instagram.com/p/Cpm_HwsrfT3/?igshid=NGJjMDIxMWI=

[immortalsins]

i’m free................survived a whole year and only almost dropped out twice

[roseinthestars457]

designing a pcb for class… what do you MEAN the h bridge will send 12V to my encoder bit and ruin my board

[electronicconference]

Analog Integrated Circuits Analog Integrated Circuits (ICs) are electronic circuits that process continuous signals, such as voltage or current, as opposed to digital circuits, which operate with discrete levels representing binary values (0 and 1). Analog ICs are designed to perform functions like amplification, filtering, modulation, demodulation, and signal conditioning. These circuits are essential components in various electronic systems, including audio amplifiers, sensors, communication systems, and power management circuits.

Nomination Link :https://x-i.me/emcnom Get Connected Here: ================== Facebook : https://www.facebook.com/profile.php?id=61556074815651 Twitter : https://twitter.com/PencisE28647 Pinterest : https://in.pinterest.com/electronicconference/

[ardl]

a single voltage buffer could probably drive 2 opamps right

[niconiconwo]

Got a nice simple 555 circuit going together and it's shaking the rust from my brain. Even the basic stuff is pretty fun.

[fuzzkaizer]

Ibanez - GA-10 - MICRO TEACHER

"I’m assuming from the opamp chip that it’s a ‘79 Ibanez GA-10 Micro Teacher mini amp, a precursor to the TS-808 circuit and what helped name it."

cred: facebook.com/Louis Durand

[slowrotation]

Tennis for Two (1958), the first video game ever, displayed on an oscilloscope. There is no source code, since it was implemented entirely in hardware. There are relays that control the direction of the ball, comparators that detect when it hits the ground or the net, opamps that implement the differential equation for the bounce of the ball, resistors that simulate drag, and so on.

[allie-leth]

Opinions on opamps?

Never actually used one in my projects, will try to fix that.

[thekingofgear]

Hey I just need to say absolutely adore your work here it has helped people such as me soo much on pretty much everything you need to know about their gear and I wanted to ask if I can’t spend that much money on an Marshall shredmaster what pedal can you recommend that is cheap that delivers that Marshall in a box sound as I bought an fender 85 today and I’m just stuck on what pedal to pick that is student budget friendly and can you possibly help with what amp settings jonny used in glastonbury 2003? Help would be much appreciated!

Just get a used ProCo Rat (standard version) and focus in your playing. Jonny didn't use one, but there's a reason so many people think he did: with the filter knob set right, the Rat has a similarly focused tone to the Shredmaster in the mids and highs.

The Shredmaster and Rat both use opamp hard-clipping followed by diode soft-clipping, so it's not a surprise they're similar (however, the Shredmaster has two stages of opamp clipping). The Rat lacks the post-clipping bass boost of the Shredmaster, but you can compensate for that with amp settings. Obviously, the Rat is less versatile than the Shredmaster, since it can't create scooped tones. But it does a good job of Jonny's favorite Shredmaster setting: contour knob at minimum for full mids and no scoop.

A bonus of getting a cheap, used Rat is you can quite easily modify it with a "clipping" switch, which gives access to Turbo Rat tones (the Turbo was Thom's favorite drive in the 90s, and that's probably the reason people used to think Jonny used a regular Rat). You can also get a Turbo Rat and add a switch for regular Rat tones, but the Turbo is usually pricier. Or, if you're particularly interested in soldering, you can build a mini Rat clone for about the price of a used regular Rat.

A shot of Thom about to stomp on his ProCo Turbo Rat during 2+2=5 on the Jonathan Ross show on November 7, 2003 (youtube).

Another Radiohead-related option is a Boss OD3, one of Jonny's favorite overdrives since ~2006. The OD3 has a distinctive tone of its own, but with the tone set right it has a bit of Marshall flavor too. And, like the Shredmaster, it has a post-clipping bass boost for a fuller sound. I also think it's a nice starter pedal, since it's more dynamic and "amp-like" than the Shredmaster and Rat (that's due to the OD3's discrete-opamp soft-clipping circuitry). It's quite usable from low to mid to high gain, so it could easily be your only drive pedal.

For settings, check the Fender Eighty-Five entry on Jonny's amplifiers page. But remember: even replicating his settings exactly will still sound different from studio recordings, because you're missing the signal chain after the amp's speaker (mic, EQ, compression, gates, etc). So (as always) it's better to use your ears and tweak the settings to find those sounds. We discuss this in more detail in this post.

A photo of Jonny performing with Radiohead in Kansas City in 2012 (Jason Squires). You can see his Shredmaster and his OD3 on the board on the left.

[pedaloftheday]

On this fine Sunday morning, we've got another sweeeeet pedal from Twilight Pulse Audioworks - the Proxima Overdrive Fuzz!! This one is is fully hand built with high-quality through hole components, clips with a pair of NOS RFT Silicon Diodes, and operates using an obsolete NOS Harris/Intersil CA3260E BiMos Opamp…check out our demo video below, cheers!!

[edisonsciencecorner]

IR line sensor array for Line follower robots #ir #linefollower #linefollowerrobot #make #diy #pcb #pcbassembly #pcbdesign #electronics #robotics #electronicsengineering #jlcpcb #opamp #irled #diyproject https://www.instagram.com/p/Cph8pyrLGcN/?igshid=NGJjMDIxMWI=

[crescent-cubed]

I went into music tech to make music on my puter, not fuck around with whatever the hell an opamp is