Free Circuit Diagram

A crystal tester circuit is very simple, it contains only oscillator and detector inside. This crystal tester circuit uses one transistor for the oscillator and one transistor for the detector. Here is the schematic diagram of the circuit: The mechanism of this crystal tester is very simple. If a good crystal is connected [...]

Crystal Colpitts oscillator can be implemented using a transistor and a parallel mode crystal. Here is the schematic diagram of  the circuit: In this circuit, the crystal acts as an inductance. A large value capacitive divider is used between gate, source, and ground, and a small series capacitor is placed in the crystal [...]

The temperature of a quartz crystal for oscillator should to be kept constant to operate at very stable frequency. This oven temperature controller is suitable for such purpose.  Here is the schematic diagram of the temperature control circuit: Although this circuit is small and simple, the design use a PWM output to preserve [...]

This is a Colpitts-crystal oscillator circuit. It is suitable for low frequency crystal oscillator circuits. Using the 2N3823 JFET, this circuit has excellent stability because the temperature will not vary the 2N3823 JFET circuit loading. Here is the circuit : [Source: National Semiconductor Application Note]

Op-amps has been widely used in low frequency oscillator (frequency <= 100kHz), but we can actually use it for high frequency crystal oscillator as long as we have an op-amp with the proper bandwidth. An excellent gain stages can be implemented using LT1190 and LT1191 op-amps. Here is the schematic diagram of the circuit: [...]

This circuit is a simple crystal oscillator that can be operated in overtone mode. Overtone mode permit the operation at higher frequency than specified by the crystal. The circuit uses a grounded base amplifier configuration, and place the crystal as a series resonator. The transistor Q1 is biased in the active region as [...]