Voltage to Frequency

The V/F converter in Figure 1 is unique because it draws less than 30 µA from one unregulated supply while converting bipolar input voltages. It produces three CMOS-compatible, 0- to 10-kHz outputs: one (F+) that becomes active when the input voltage is positive, another (F­) that takes over for negative inputs, and a third (FABS) that produces a frequency proportional to the absolute value of the input...

This is a voltage controller oscillator that was designed as a wide range oscillator to generate clock pulses for a stepper motor drive system. It does however have some interesting features. The original application used a stepper motor for its ability to operate over a very wide speed range, so this oscillator is also designed for a very wide frequency range. The prototype could be varied over 1,000,000:1 - six decades...

The output frequency of the simple VCO in Figure 1, which is synthesized from inverting latch stages, is tunable to an integer multiple of the input frequency by selecting which output phases feed back to the input multiplexer. The circuit has worked successfully in on-chip clock multiplication in ASICs. The number of latch stages that you can cascade in a real-world design limits the multiplication factor...

The inspiration for the VCO in Figure 1 came from Texas Instruments application notes of years ago, detailing the use of unbuffered U-type inverters for use in ring oscillators. The application notes circuit consists of only the inverters. The circuit generates relatively squarish waveforms. Any ring oscillators operation depends on the fact that an odd number of inversions exists around the loop...

The best of the monolithic voltage-to-frequency (V/F) converters have performance thats so good it equals or exceeds that of modular types. Some of these ICs can be designed into quite a variety of circuits because theyre notably versatile...

Single-phase induction motors are extensively used in appliances and industrial controls. The Permanent Split Capacitor (PSC) single-phase induction motor is the simplest and most widely used motor of this type. The classification, construction and working principle of single-phase induction motors are explained in detail in the application note "AC Induction Motor Fundamentals" (AN887) available from Microchip...

This circuit uses a CMOS version of the classic 555 timer, to form a light intensity to frequency converter. A small PIN photo diode is used as the light detector. The pulses produced are short, so in some applications you may want to stretch them or feed them through a flip/flop to produce a square wave signal. Although the circuit shown is designed for a 5v supply, it could operate from almost any voltage from 3v to 15v...

If you need a clean emitter coupled logic (ECL) type signal between 200MHz and 400MHz this circuit works fine. It uses four voltage-controlled capacitors to change the frequency...

By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1. A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal...

No description available...

This application note is intended to show a general solution for implementing a low cost A/D and a 2-way multiplexed LCD drive using National Semiconductor`s COP840C 8-bit microcontroller. The implementation is demonstrated by means of a digital personal scale. Details and function of the weight sensor itself are not covered in this note...

Figure 1 shows a voltage-to-frequency (V/F) converter that produces a 0- to 10-kHz output for an input range of 0 to 5V. Linearity of the converter is 0.02%, and gain drift is 60 ppm/8C. The maximum current consumption is only 26 µA, 100 times lower than currently available units. To understand the circuit`s operation, assume that the voltage at IC1`s negative input is lower than the voltage at its positive input (IC2`s output is low)...

Figure 1, below, shows the 10.58 to 10.74 MHz VFO oscillator circuit. Yes, this is the same circuit that was presented last time, but Ive re-drawn it to show the Colpitts oscillator more clearly. "L" is approximately 1.5 uH; 19 turns in a T50-6 core (yellow). The value of C6 is found experimentally. I used 69 pF (a 47 pF and a 22 pF in parallel). More about this during check-out...