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F-V convertors applications: Tachometer in motor speed control Rotational speed measurement.

**Frequency
to Voltage (F-V) and voltage to frequency convertors (V-F)**

Â·
F-V
convertors applications: Tachometer in motor speed control Rotational speed
measurement.

Â·
Two
types of it: Pulse integrating Phase locked loop

Â·
F-V
convertor produces an output voltage whose amplitude is a function of input
signal frequency.

Â·
V_{0}=k_{f}
f_{i} kf is sensitivity of F-V
convertor

Â·
It
is basically a FM discriminator.

Input
frequency is applied to comparator A.

Resistor
R acts as feedback element.

Capacitor
Ci enables charge-balancing,

High
pass network conditions input signal

For
negative spike of V 01, comparator COMP triggers one shot multivibrator with
threshold 7.5V The output of multivibrator closes the switch SW, for a time TH,
this causes voltage Vo to build up and inject thru R and this continues until
current out of summing input of opamp is equal to that injected by Vo through R
continuously.

Vo=10^{-3}
*T_{H} *R*fi as T_{H} =7.5 C /1X10^{-3}

Ripple
Voltage, Vr(max) =7.5 C /Ci

**Principle: **Charge balancing technique-the
process of charging and discharging results in frequency** **proportional to input signal F0= k Vi

**Operation**: Op-amp A converts input V_{i}** **to current I_{i}** **= V_{i}/R into summing
junction.

When
switch SW is open the current flows into capacitor Ci and charges it, and node
voltage V_{o1} produce ramp down.

When
V_{01} =0 CMP triggers and sends a triggering signal to one shot
multivibrator that closes the switch SW and turns transistor Q ON for time T_{H}.

The
threshold of mono shot = 7.5 V and T_{H}= 7.5 C/10^{-3}

During
T_{H} , V_{01} ramps
upward by amount âˆ†V_{01}=(1mA-I_{i}) T_{H }/C_{i}

Time
duration TL for vo1 to return to 0 is TL =
Câˆ†V_{01}/I_{i}

T_{L}+T_{H}
= 1mA T_{H} /I_{i} = T

F_{0}=V_{i}/7.5
RC

Tags : Ideal characteristics, Principle, Operation , Linear Integrated Circuits : Waveform Generators and Special Function ICs

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Linear Integrated Circuits : Waveform Generators and Special Function ICs : Frequency to Voltage (F-V) and voltage to frequency convertors (V-F) | Ideal characteristics, Principle, Operation

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