Micro Power AM Broadcast Transmitter
The circuit employs the 74HC14, which is a high-speed CMOS hex inverter featuring Schmitt trigger inputs. This component is ideal for generating square wave signals due to its hysteresis characteristics, which provide clean transitions between high and low states, minimizing noise and ensuring stable oscillation.
In the VFO configuration, the 100pF capacitor is connected in parallel with a resistor, forming an RC timing circuit that determines the frequency of oscillation. The frequency can be calculated using the formula f = 1 / (2 * π * R * C), where R is the resistance and C is the capacitance. By varying the resistance, the frequency output can be adjusted to meet specific application requirements.
The output from the 74HC14 is connected to the base of a small signal transistor, which operates in class C mode. In this configuration, the transistor conducts for less than half of the input signal cycle, allowing it to amplify high-frequency signals efficiently. Class C amplifiers are known for their high efficiency, making them suitable for RF applications.
The transistor's collector is connected to a load, which could be an antenna or another stage of amplification. Proper biasing must be applied to the transistor to ensure it operates within the desired parameters. This circuit can be used in various applications, including RF transmitters, signal generators, and other electronic devices requiring square wave oscillation and amplification. Proper layout and component selection are essential to ensure reliable operation and minimize distortion in the output signal.In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration. The oscillator frequency can be either fixed by a crystal or made adjustable (VFO) with a capacitor/resistor combination.
A 100pF capacitor is used in place of the crystal for VFO operation. Amp.. 🔗 External reference
Related Circuits
Most devices used in amplifier output stages exhibit significant non-linearity, with transistors (both bipolar and FET) being particularly problematic. These components are almost always employed within a global feedback loop to mitigate their non-linear characteristics. Similarly, tetrode and pentode...
This compact circuit transmitter processes audio signals from a table or microphone, as well as video signals from a camera, DVD, or video cassette. It can transmit these signals directly from a computer over a free VHF channel. The...
This document discusses the use of small microcontrollers, such as those from the PIC and Atmel series, which typically operate at 5V and require less than 100mA for complete system functionality. Some PICs can function at lower voltages, such...
This series utilizes the TDA2822M integrated circuit (IC) as the primary amplifier. Additionally, alternative ICs such as KA2209, NJM2073, U2822B, and U2823B can be employed alongside the TDA2822M. The output power is limited to a maximum of 4 watts,...
Frequently, the output current of an operational amplifier is inadequate for applications such as driving a small motor or loudspeaker. This issue is typically resolved by adding an emitter follower to the circuit. However, this configuration does not allow...
The following diagram is the schematic for a variable power supply that delivers an output voltage ranging from 0 to 28V at a current of 6/8 A. The component part list includes: R1 = 2.2 kΩ, 2.5 Watt; R2...