In the calculator we enter the desired RF frequency which is 88MHz and also enter the value of the two capacitors which is 47pF and 5pF. For this we use the Oscillator Online Calculator and select the Colpitts oscillator. To calculate this number of turns required for given coil diameter first we need to calculate the inductor inductance required value for given frequency and two capacitor values. The coil inductor is made of 10 turns with 4mm diameter. Using this technique, a single transistor or JFET can achieve circuit gains of 20,000 easily. Here the value of the L1, C4 and C3 are such that the oscillator oscillates at 88MHz. The value of L1, C4 and C3 are chosen such that it oscillates in the FM frequency range which is 86 to 106MHz. Figure below shows a low-parts-count FM radio based on a TDA7021T integrated circuit by NXP. The oscillator circuit is made up the second BC547 transistor configured with inductor L1, C4 and C3 in colpitts oscillator configuration. Default Amplifiers Audio and Radio Attenuators Clocks and Timing Diodes Front-End Modules Isolation Modems And DAAs Optocouplers Power Management. Crystal radio with one transistor audio amplifier, base-bias. The amplified signal is then coupled into the oscillator circuit using the electrolytic capacitor C2. The pre-amplifier amplifies the small audio signal of around 10-15mV amplitude from the microphone to higher amplitude. The VHF super regenerative receiver has been trimmed down to a single transistor without compromising its tremendous sensitivity and selectivity while maintaining the same clear audio. The tutorial Testing of self biased BJT amplifier on breadboard with PC oscilloscope shows how to design and test self biased amplifier. Regenerative FM Receiver Using One Transistor. The first transistor Q1, the BC547 transistor, which is biased using self biasing method with resistors R2 and R3 is the pre-amplifier. The audio enters the pre-amplifier via the coupling capacitor C1. This FM transmitter circuit uses four radio frequency stages: a VHF oscillator built around transistor BF494 (T1), a preamplifier built around transistor. Audio enters the transmitter through this microphone. R1 is required to power up the microphone because the electret microphone has a FET(Field Effect Transistor) inside it which requires power. In the above circuit diagram, MIC1 is the electret condenser microphone.
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