Amplifier Gain and Frequency Response Using AI

電子學問題ＡＩ求解方式

standard strategy

  AI for solving amplifier electronics (課堂講義內有參考解答)

solve for gain

do not ignore bias current

calculate miller effect

calculate poles for lower cut off

calculate poles for higher cut off

plot bode plot gain vs. Hz

plot bode plot phase vs. Hz

Solve for the gain. Plot frequency response for the following amplifier circuit.

Source

artifact

AI Model Results:

• Grok 4: Share Link (considers parasitic capacitance Cπ ≈ 50 pF, Cμ ≈ 2 pF) - Bode Plot (188 kHz)
• Claude: Bode Plot gives 188 kHz, 
• ChatGPT 5: Share Link gives 187 kHz
• Gemini 2.5 Pro: Share Link gives 188 kHz

Note: Lower cut-off comes from coupling capacitors (not shown here).

Generate professional grade Bode plot.

Using AI tools to generate professional plot using Matplotlib

Bode plot

ChatGPT integrates Python environment so it directs generates Bode plot.

Bode plot

React (Claude) - Python w/Matplotlib -  - Colab - Plot

Colab

Bode plot 

1. React (Claude) - AIStudio - Python w/ Matplotlib - Colab - Plot

2. Reasoning (AIStudio) - AIStudio - Python w/ Matplotlib - Colab - Plot

我用Claude計算電晶體放大器，得出頻率響應理論值 2.4 MHz。然後我給他一組Grok 算出來的數據是 125 kHz，兩者差了20倍。

我沒有跟Claude 說這組數據哪裡來的，他稱讚我的數據是應該是用Spice 專業軟體跑出來的，而且提醒我他的計算是根據純理論，因為Spice 可以考慮更多細節去電路模擬，所以Claude認為我的數據比較值得參考。

接下來我跟他講這組數據是 Grok 4 算的，Claude 馬上變換語氣，說頻率響應不可能是125 kHz，業界標準至少在1 MHz 以上，說Grok:

1. Does not make any sense (完全沒有道理）
2. Against common sense (違背常識）
3. Distrust (不值得信賴）

可是剛剛不是還在稱讚「我的模擬」做得好？以前Claude 還會稱讚別家的AI有什麼優勢，現在看起來不演了。

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Amplifier Circuit Analysis

Solve for the gain, plot freq response.

Share (Source)

share (Claude running Python internally on VM)

• Hybrid-π Model, With bypass capacitors, without ignoring base current loading effects on bias networks, Av=-165 (Share including frequency response).
• -194 for Vc vs. Vbase, Ibase ignored (Share)

Gemini 2.5 Pro gain & lower cut off freq match Claude, 4kHz.

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Solve for the gain. Plot frequency response for the following  amplifier circuit.

Source

share (Av=-2.31, Lower Cutoff 20 Hz, Upper Cutoff 10.46MHz)

Analysis with Cπ = 22.1 pF, Cμ = 3.0 pF

20Hz is assumed, not by calculation

Analysis with Cπ = 22.1 pF, Cμ = 3.0 pF: 

• Bode plot, fH = 10.46 MHz, RE not bypassed

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Two-Stage Amplifier Analysis

Solve for the gain, plot frequency response.

Source

Schematic

colab unoptimized (share)

colab optimized (share)

colab increasing C2 from 1 to 10μF (other parameters differ from above)(share)

bypass 47, coupling 10 micro F

(gain approximate)

• Artifact, Share (Cπ2=15 pF, Cμ2=3pF). Result: freq response, gain=8513, low cut off=46.5 Hz, high cut off=312kHz
• Gemini: Result gain=8509, low cut off=46.5 Hz, high cut off=296 kHz @Cπ2=15 pF, Cμ2=3pF (good match!)

Compare

• Artifact, Share. Result: gain=8559 (Hybrid-π Model, With bypass capacitors, without ignoring base current loading effects)
• Artifact. Result: gain=9460 (Ignored base current loading effects)
• comprehensive comparison simplified, do not ignore bias network, do not ignore base current

Can we ask for Bode plot without finding lower/higher cut-off freq?

• You'd better not. (calculated by AIStudio)

Can we be more accurate with cut-off freq? Yes, use transfer function. 296kHz becomes 235kHz. (based on AIStudio)

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Design a Two-Stage BJT Amplifier

Use A* search for optimization. optimal schematic

share

Performance metrics (share)

Use A* to design a class AB amplifier.

The first stage is class A. the second is class B. freq response cut off at 10Hz and 25 KHz

artifact (share)

schematic enhanced by Gemini 3.0 Pro

artifact enhanced by Claude (share)