Frequency Modulated Oscillator (for FM Transmitter)

An oscillator can be built using LC (inductor-capacitor) tank circuit. When we vary the capacity of the capacitor in LC tank circuit then the frequency of the oscillator will vary according to capacitance change.  The idea of this modulator is by employing a varactor (voltage-dependent variable capacitor) in the LC tank circuitry. As the capacitance is controlled by a voltage […]

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Voltage to Frequency Converter Using UJT

The following voltage to frequency converter (V/FC – VCO) circuit consist of a UJT (uni-junction transistor) oscillator in which the timing charge capacitor C2 is linearly depends on the input signal voltage. The voltage across resistor R5 set the charging current, which is accurately controlled by the amplifier. Here is the schematic diagram of the circuit:

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Digitally Programmable Oscillator

The schematic diagram below shows a digitally programmable oscillator circuit. This programmable oscillator circuit is based on V/F (voltage to frequency) converter, which is programmable by an analog voltage at the input. To make it digitally programmable, a DAC (digital to analog converter) is added to feed the V/F input. The components of the DAC is AD7520 multiplying D/A converter […]

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