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Analog Oscillator
Analog Electronics
An analog circuit demonstrating how transistors can operate as solid-state switches while resistor-capacitor pairs control oscillation.
Type
Analog Circuit
Switching
NPN 3904 Transistors
Timing
Resistor + Capacitor
Output
Blue LEDs
Development
Breadboard + PCB
Project Context
The Analog Oscillator was developed to demonstrate how a transistor can be used as a solid-state switch. The project progressed through a breadboard prototype, an ACES PCB, and a final enclosure.
Reference
01
Two transistors alternate between on and off states as the capacitors charge and discharge, producing a repeating square-wave signal.
The resistor and capacitor pairs affect the length of the oscillation. The transistors automate the blinking LEDs as the capacitors charge and discharge below 0.65V.
The resulting circuit provides a constant square-wave signal that can be used in future projects requiring this type of output.
02
Two NPN 3904 transistors operate as solid-state switches within the oscillator.
Each transistor has three leads: base, collector, and emitter. When voltage is applied to the base lead, the transistor closes. When no voltage is present, the transistor remains open.
When the circuit is turned on, one transistor is on while the other is off. The two capacitors allow these states to alternate.
03
Alternating capacitor charging controls the two transistors and creates the repeating output.
Negative voltage from a capacitor turns one transistor off while the other capacitor begins charging.
Once the second capacitor is charged, it turns off the second transistor and the first capacitor begins charging again. The process repeats and creates square-wave signals.
04
Development began by assembling the complete oscillator circuit on a breadboard.
A schematic was followed to assemble the circuit. The main components were two NPN 3904 transistors, two 100 µF capacitors, two 1 kΩ fixed resistors, and two 10 kΩ fixed resistors.
Breadboard Prototype
Initial analog oscillator circuit
05
After breadboard testing, the circuit was soldered onto an ACES PCB.
Soldering the Analog Oscillator required additional care because the circuit contained multiple polarized and heat-sensitive components.
ACES PCB
Soldered analog oscillator circuit
06
The completed PCB was installed into its final case using heat synced rivets and four mounting screws.
The soldering iron was heated to 300°C and the heat synced rivets were sunk into their holes by applying light pressure with the iron.
The power jack was then installed and wires were soldered to the completed PCB before four screws were used to mount the PCB into the case.
07
Breadboard Parts Table
Qty.
9V DC Alkaline Battery
1
ACES Power Jack
1
1 kΩ Fixed Resistor
2
10 kΩ Fixed Resistor
2
5mm Blue LED
2
100 µF Capacitors
2
NPN 3904 Transistors
2
Wires
Assorted
08
The completed Analog Oscillator combines transistor switching and resistor-capacitor timing in a permanent soldered circuit.
Analog Oscillator
Completed project
Internal Circuit
PCB and circuit assembly