Free Circuit Diagram

Using LM231/331 chip, we can build a low-cost voltage-to-frequency converter, ideal for analog-to-digital conversion, frequency-to-voltage conversion, long-term integration, linear frequency modulation-demodulation, and many other functions.  When it’s used as voltage-to-frequency converter, the output will be a pulse train with frequency linearly equal to the applied input voltage. For higher level of accuracy against temperature drift, [...]

Metal Detector Circuit Topology One of the simplest method of metal detecting is by beat frequency oscillator. Basically, the circuit consist of two balanced oscillator. One oscillator provides the reference signal, and other oscillator is acting as the detector element. The reference oscillator’s frequency is fix, while the detector oscillator is variable depending on [...]

This sine wave generator is adjustable between 15 Hz to 150 kHz. The circuit is basically a Wien-bridge oscillator, with multiple capacitor selection. Here is the schematic diagram: A stereo 10k potentiometer is used to control the frequency. The dashed line connecting these two potentiometers show that both potentiometer has single axis.

This is a circuit of voltage controlled variable gain amplifier. This circuit uses 2N4391 that will provide a low Rds(on) less than 30 Ohm. This circuit also uses a tee attenuator, that will provide optimum dynamic linear range for attenuation. We can obtain the attenuation greater than 100dB at 10MHz by providing proper RF construction [...]

Using VFC110 chip, we can build a high frequency voltage-to-frequency converter. The features of this chip include the capability of high frequency operation, disable function, and an on-board precision 5V reference. This precision reference can be used to provide reference for offsetting the VFC transfer function, as well as provide transducer or bridge excitation. As [...]

Frequency meter can be used in speed sensor, tachometer, or any measurement of repetitive signals. This frequency to voltage converter (FVC) can be used to turn your analog or digital voltmeter into a tachometer. The circuit’s schematic diagram is shown below. The circuit consist of three blocks. The first block is a squarer, [...]