Crystal tester circuits using BC107

Description: A multimeter cannot be used to test a crystal oscillator. Instead, a dedicated circuit is required, capable of checking crystals within the frequency range of 100 kHz to 900 MHz. This circuit is easy to construct and cost-effective.

To construct a crystal testing circuit that operates effectively within the specified frequency range, several key components and design considerations must be included. The circuit typically consists of an oscillator circuit, such as a Colpitts or Hartley oscillator, which utilizes the crystal under test as part of its frequency-determining network.

The oscillator can be built using a combination of transistors or operational amplifiers, depending on the desired output characteristics and complexity. For instance, using a bipolar junction transistor (BJT) in a common-emitter configuration can provide sufficient gain and frequency stability. The crystal is connected in parallel with the feedback network, ensuring that the oscillator operates at the crystal's resonant frequency.

To facilitate measurements, a frequency counter or an oscilloscope can be employed to observe the output frequency. A simple LED indicator can also be integrated into the circuit to provide a visual confirmation of oscillation. The circuit may require additional components such as resistors, capacitors, and possibly a variable inductor to fine-tune the frequency response.

Power supply considerations are also crucial; the circuit should be powered by a stable DC source to prevent fluctuations that could affect the oscillator's performance. It is advisable to include decoupling capacitors close to the power supply pins of active devices to minimize noise.

Finally, a printed circuit board (PCB) layout can be designed to ensure that the connections are neat and that parasitic capacitances and inductances are minimized, which is particularly important at higher frequencies. With careful design and assembly, this crystal testing circuit can provide reliable performance for a wide range of crystal frequencies.You cannot use a multimeter to check a crystal. You should have a this circuit, because it can check a crystal 100Khz to 900Mhz, easily to make and cheap.The..