Adjusting RV1 Potentiometer
CHANGE RV1 PY POTENTIAL METER
Thought for 9 sec
I’ll update RV1’s potentiometer setting in-place if it’s just a value/property change; first I’ll inspect RV1 to confirm its current part and editable properties, then apply the change and verify it.
Thought for 26 sec
RV1 is already a through-hole Bourns 3386P vertical potentiometer/trimmer, wired for base bias. I don’t need to replace it because replacing would risk breaking its existing connections; I’m just verifying the current state now.
Thought for 43 sec
RV1 is already a 10k through-hole potentiometer/trimmer: Bourns 3386P-1-103LF. I verified it is wired correctly for base bias: pin 3 to 12V, pins 1 and 2 tied to the BASE_BIAS node, so no replacement was needed.
Use panel-mount pot
Find smaller trimmer
Check RV1 footprint
Verify RV1 design
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Amplifier Design Notes
Source Circuit
The project recreates the uploaded common-emitter audio amplifier reference as a PCB-oriented design.
Implemented Schematic
- Q1: 2N2222A NPN transistor, TO-92. Datasheet pinout used: 1 = Emitter, 2 = Base, 3 = Collector.
- J1: 12 V DC input terminal, pin 1 = +12 V, pin 2 = GND.
- J2: audio input terminal, pin 1 = signal, pin 2 = GND.
- J3: speaker/output terminal, pin 1 = AC-coupled output, pin 2 = GND.
- R4: 100 ohm collector resistor from +12 V to collector.
- R3: 10 ohm emitter resistor from emitter to GND.
- R2: 470 ohm base-bias resistor from base to GND.
- RV1: 10 kOhm trimmer wired as rheostat from +12 V to base node; pins 1 and 2 tied to base, pin 3 to +12 V.
- C2: 100 uF input coupling capacitor.
- C1: 1000 uF emitter bypass capacitor.
- C3: 470 uF output coupling capacitor.
- C4: 100 nF supply bypass capacitor across the 12 V input.
Datasheet Validation
2N2222A datasheet checks performed during final validation:
- Pinout: 1 = Emitter, 2 = Base, 3 = Collector for the TO-92 package.
- Absolute maximum collector-emitter voltage VCEO: 40 V for 2N2222A.
- Absolute maximum collector current IC: 600 mA.
- Power dissipation Ptot: 625 mW at 25 C.
- DC current gain hFE: min 75 at VCE = 10 V, IC = 10 mA; 100 to 300 at VCE = 10 V, IC = 150 mA.
Final PCB / ERC Review Status
Fresh review run on 2026-05-15 showed no ERROR, WARNING, or OPEN review checks. The PCB layout is configured as a 50 mm x 50 mm rectangular 2-layer board with all 12 physical components placed on the top side and routed. No unresolved airwires or blocking DRC/ERC issues were reported in the final review.
Simulation Result Summary
Simulation was run with +12 V supply, RV1 modeled at its full 10 kOhm from +12 V to base, R2 = 470 ohm, R3 = 10 ohm, R4 = 100 ohm, and an 8 ohm speaker load through C3.
DC Operating Point
- Base voltage: 0.5386 V.
- Emitter voltage: 0.000184 V.
- Collector voltage: 11.998 V.
- VCE: 11.998 V, so the transistor is not saturated.
- Collector current: 18.18 uA.
- Base current: 0.180 uA.
- Simulated DC beta: about 101.
Audio Output Into 8 Ohm
- Gain at 20 Hz: about -45.94 dB, or 0.00505 V/V.
- Gain at 1 kHz: about -45.67 dB, or 0.00520 V/V.
- Gain at 20 kHz: about -45.67 dB, or 0.00520 V/V.
- For a 10 mV AC input at 1 kHz, output amplitude is about 52 uV.
Engineering Warning
The PCB and ERC/DRC validation are clean, but the circuit as drawn is not a practical 8 ohm speaker amplifier. With RV1 at 10 kOhm, Q1 is biased very close to cutoff and the output is effectively inaudible. The 8 ohm speaker also AC-loads the collector very heavily: 100 ohm || 8 ohm is about 7.4 ohm, which collapses the common-emitter voltage gain.
Recommendation
Use this design as an educational/common-emitter demonstration or as a high-impedance preamp experiment. For a usable speaker amplifier, revise the design to add a proper output stage, such as an LM386-class audio amplifier, a complementary push-pull emitter follower, or a small class-D speaker amplifier. If the requirement remains direct 8 ohm speaker drive, the schematic should be revised before manufacturing.
Source Circuit
Implemented Schematic
Datasheet Validation
Final PCB / ERC Review Status
Simulation Result Summary
DC Operating Point
Audio Output Into 8 Ohm
Engineering Warning
Recommendation
