Free Circuit Diagram

A  laser diode driver can be implemented using voltage-controlled current source.  This simple  linear laser diode driver gives cleaner drive current than a switched (PWM) drivers. Here is the schematic diagram of the circuit: A Howland current pump with a current booster is used as the basic of this laser diode driver. Q1 [...]

This FM transmitter circuit is small, similar to our previous single chip FM  transmitter, but this FM transmitter is monophonic. You can see in the circuit’s schematic, the left and right signals is mixed before modulate the radio frequency. Here is the schematic diagram of the circuit:   The core of this [...]

A PLL system can be used to implement an FM demodulator. When a PLL is locked on an FM signal, the VCO tracks the instantaneous frequency of that signal. Since the VCO output tracks the FM signal, and the VCO input voltage is proportional to the VCO output frequency, then the VCO input will be [...]

This is a FM Transmitter circuit. This circuit uses logic gates. This transmitter circuit has a RF oscillator. This oscillator uses 10.7Mhz ceramic filter and inverter N2 to drive the parallel combination of N4 to N6 through N3. Here is the circuit: The output impedance will be low because these inverters are [...]

Please be warned if operating this circuit might violate the regulation of your country, because this FM transmitter circuit radiate strong radio frequency to the environment. This wireless microphone is very sensitive, pick up every sound in the 20m radius, and transmit the radio signal up to 2 kilometers in open air. Here is the [...]

The excellent high input impedance, high slew rate, and high voltage qualities of CA3140 op-amp make it suitable for Wien-bridge sine wave oscillator. The basic circuit for Wien-bridge sine wave oscillator is shown in the figure below (the upper part). You can see the formula in the figure, when R1=R2=R, and C1=C2=C, then the formula [...]