I tried a simple experiment. I looked up a tutorial on class A amplifier design at this link:
https://www.electronics-tutorials.ws/amplifier/class-ab-amplifier.html
I also downloaded the datasheet for a 2N3904 Transistor. I first informed ChatGPT that I would paste the tutorial and the datasheet into the chat. Then, I asked it for the component values to make an audio preamp using a 2N3904 transistor. It read the article, learned what to do, and then did the math based on the datasheet. You can then ask more questions, like changing the gain and impedance.
Even if not perfect, it was really cool to do and a nice jumping-off point.
Here is the Response:
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For an audio preamp with a 20 Hz to 20 kHz frequency response and a 600 ohm output impedance, we can make some more precise component value selections to achieve a suitable design. Additionally, assuming a high impedance input, we can target a voltage gain of around 10 (20 dB) for this example. Keep in mind that specific design requirements and preferences may lead to different component values.
Component Values:
1. Transistor: 2N3904 (Silicon NPN transistor, as provided in the data).
2. Input Coupling Capacitor (C1): To achieve a 20 Hz to 20 kHz frequency response, a capacitor with a lower cutoff frequency should be used. Let's choose C1 ≈ 4.7µF.
3. Emitter Resistor (R1): We can set the biasing current for the transistor to a reasonable value, such as Ic ≈ 1 mA. Assuming Vbe ≈ 0.7 V, we can calculate R1 ≈ (Vcc - Vbe) / Ic ≈ (9 V - 0.7 V) / 0.001 A ≈ 8.3kΩ. We can choose a standard resistor value of R1 ≈ 8.2kΩ.
4. Emitter Bypass Capacitor (Ceb): To improve low-frequency response, we can add a bypass capacitor in parallel with R1. Let's use Ceb ≈ 10µF.
5. Collector Load Resistor (R2): To achieve a voltage gain (Av) of 10 (20 dB), we can use the following formula: Av = - R2 / R1. Solving for R2, we get R2 ≈ - Av R1 ≈ - 10 8.2kΩ ≈ - 82kΩ. Since R2 should have a positive value, we can choose R2 ≈ 82kΩ.
6. Output Coupling Capacitor (C2): To allow the AC audio signal to pass through, we can choose C2 ≈ 4.7µF (similar to C1).
7. Load Resistor (R3): To match the 600 ohm output impedance, we can set R3 ≈ 600Ω.
Please note that the values above are calculated based on typical design considerations and assumptions. Depending on specific component availability and desired performance, it may be necessary to adjust the values slightly. Additionally, a suitable power supply should be provided to bias the transistor and provide the necessary voltage levels for the preamp circuit.
Remember to simulate the circuit and test it before building to ensure that it meets your requirements and provides the desired audio performance.
If you have any further questions or need additional assistance, feel free to ask!
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I used the free version of ChatGPT
I agree with you. My old Post was actually about using chatgpt to help design something, let it do the math and so that's why I posted the conversation, not so much to replace my words. I actually haven't tried doing what the thing suggested, but recently it really helped me understand why my circuit is behaving like it is. But anyway if I do use the output from it is to get suggestions about whether it's right