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VCO – Voltage Controlled Oscillator using Opamps

This is a Voltage to pulse converter using opamps for measuring speed or rate from a Tacho Motor mechanical coupled to a Conveyor System.

See the complete circuit in my site to study other sections. The motor DC out is filtered and scaled. Then the clean safe dc is fed to this VCO based on a generic application note design.

The pulses can be used to advance digital counter or mechanical counter using a solenoid driver transistor circuit. The Voltage Vin can be further scaled and fed to a Digital Panel meter to read the rate. VCO - Voltage Controlled Oscillator using Opamps


VCO – Voltage Controlled Oscillator using Opamps. LM339 is a quad ┬áComparator.

 The complete PDF circuit and other such circuits at my Mixed Circuits Analog with Digital

Voltage to Frequency Converter ICL8038

This was a small circuit made for driving an Impact counter. The heart being ICL8038. It must have been a Motor driving a Conveyor, the motor has a feedback attachment called Tachogenerator.

Voltage to Frequency Converter ICL8038

Only part of the circuit is shown here. See the image of product here Tacho Counter. The configuration is derived from the Application Notes of Intersil. The Voltage from Tachogenerator is Measured on a DPM-DVM and also fed to this circuit after attenuation and filtering. The square pulses of 8038 is used to derive a Logic pulse train for a CD4040. The CD4040 works of 0 and 12V. The above circuit is on +12 and -12. That is the reason R10-R15-Q1 are used. The pulses are 0-12V pulses. The Zero is Virtual like the Virtual Ground in low current power supplies.

Function Generator using ICL8038


  • Frequency range – 0.95 Hz to 105 KHz in five decade ranges
  • Waveforms – Sine, Triangular and Square.
  • Output amplitude – Adjustable from 10 mV PP. to 10 V PP
  • Output impedance – 50 ohms.

Function Generator using ICL8038


  • ICL8038 waveform generator ICL8038
  • LM318 Operational Amplifier LM318



Digital to Analog with R2R Ladder Network

This is a R-2R Digital to Analog Converter, It converts a byte (8 bit) to a analog value. It has 256 levels including zero.

This can be used to convert a byte sent from a microcontroller to a analog value like say 1.51 V. At full scale, when all 8 bits are high calibrate to give 2.55 V then ever bit increment is 0.01V, 10mV steps.

Digital to Analog with R2R Ladder Network

If the eight bits inputs are from a counter you then will see a staircase waveform at output, each step being 10mV higher or lower depending on whether the counter is counting up or down.

The accuracy of the analog output depends on the resistor ladder. The OP07 has an offset error of about 70uV only. The 74HCT373 power is derived from LM336 a stable reference so that the D-A is accurate. The 8 bit data can be latched with the 74HCT373 to get a stable analog value for control systems.