Simple Audio Amplifier Circuit — DIY Audio AmpliFier
Next-gen DIY secrets & a clear diagram — build a tiny, powerful (for its size) audio amplifier using a single C945 transistor, 1K bias resistor and a 22µF coupling cap. Perfect for hobbyists, bench testing, and quick speaker projects.
Quick parts list
| Part | Value / Note |
|---|---|
| Transistor | C945 (NPN) — general-purpose amplifier |
| Resistor | 1 kΩ — base bias resistor |
| Capacitor | 22 µF / 16V — input coupling capacitor |
| Speaker | Small 4–8Ω speaker (3–5 W) recommended |
| Battery / PSU | Single cell Li-ion ~3.7V or 3–5V regulated supply |
How it works
Audio from an AUX source passes through the coupling capacitor (22µF) to the base of the C945 transistor. The 1K resistor provides base bias. The transistor amplifies the input waveform and drives the speaker from the collector. This is a single-transistor amplifier (class A/biased) suitable for small speakers and experimentation.
Troubleshooting & bench tips
- Confirm wiring and correct transistor pinout before powering.
- Start testing with a current-limited bench supply or add a series resistor to the battery to prevent short damage.
- If the speaker is silent, check the coupling capacitor polarity and base bias resistor.
- For hiss or distortion, try increasing the base resistor or use power decoupling.
Main image — quick datasheet
| Parameter | Typical / Note |
|---|---|
| Transistor | C945 (NPN small-signal) |
| Supply | 3.0–4.2V (single cell Li-ion recommended) |
| Speaker load | 4–8 Ω (small paper cone) |
| Expected output | Low-power loudness for small speaker; not hi-fi |
Attribution: published by -gsm4files-.
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