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This is a precision 38 kHz Infrared transmitter using MOS integrated circuit uPD 6121.It uses the NEC transmission format ideally suited for remote operation in TV, VCD Player etc. The NEC transmission format includes leader codes, custom codes (16 bits), and data codes (16 bits).The frequency of oscillation is determined by the Crystal. The IR LEDs connected to the output emits IR pulses at 38kHz.The circuit is ideal for most IR Sensors since these are designed for 38 kHz pulsed IR rays.
Another great quartz crystal oscillator schematic with bb139, a 2-nd harmonic quartz crystal and one BF214 transistor. So, the Q quartz is half of the desired transmitter frequency, L1 has 24 turns, 0.08mm Ø built on a 455kHz carcase. L2 has 8-9 turns / 0.8mm Ø / 5mm Ø. This quartz oscillator circuit has a great frequency stability, I’ve build it.
Crystal quartz circuit components
A very simple crystal quartz oscillator circuit schematic which use a quartz for frequency stability and a good rf tranzistor. Use a 2-nd or 3-rd harmonic crystal , for example if you want 100MHz use a 50MHz or 33.3MHz quartz or if you want use a 4-th harmonic crystal but the output rf voltage will be lower. The L coil has 5 turns 0.8mm Ø , 6mm Ø , 1 mm step, output at first turn from + . Use C4 for fine frequency adjustments.
For a great frequency stability, this quartz oscillator circuit must use a good varicape diode (you can use bb139).
High frequency waveform generator is very useful in electronic experiment and design. This circuit generate sine wave oscillation, but actually we can modify the circuit to generate triangle or square wave function.
The core of this waveform generator is MAX038. This integrated circuit chip gives complete function to build a waveform generator/function generator.
