This circuit can be used as a signal injector or signal tracer. This circuit is very helpful in trouble shooting audio circuits, when you need to test a circuit by injecting a signal and observe the output (by watching the oscilloscope or by hearing the loudspeaker ), or by tracing some points inside the circuit when an audio signal is applied to the input.
Skema Rangkaian Audio Signal Injector|TracerThe circuit uses supply from 9 volts battery. An alligator clip is recommneded for the ground probes, so you can works with one hand to hold the board, and the other hand to target the test probes. The SPDT switch connected to the transitor and the earpiece is used to select the function, whether as a signal or a signal injector tracer.
Transistor 2n3904
This transistor is designed as a general purpose amplifier and switch. The useful dynamic range extends to 100 mA as a switch and to 100 MHz as an amplifier.
Transistor 2n3904 Pin- Collector-Emitter Voltage 40 V
- Collector-Base Voltage 60 V
- Emitter-Base Voltage 6.0 V
- Collector Current - Continuous 200 mA
- Operating and Storage Junction Temperature Range -55 to +150 °C