# How to build a Frequency to Voltage converter without microcontrollers

#### Thevenin99

Joined Mar 23, 2017
12
We are supposed to construct a Frequency to Voltage converter without using any microcontrollers, or integrated circuits. Only op amps, comparators, resistors, capacitors,inductors, voltage regulators

We were told as an example if we input a 3khz frequency we should get 3 volts in return

Any suggestions?

#### MrChips

Joined Oct 2, 2009
24,141
Sounds like homework to me.
Moved to Homework Help unless proven otherwise.

#### Alec_t

Joined Sep 17, 2013
12,197
Since this is Homework, what thoughts have you had so far for solving the problem? We can give hints, but don't do your homework for you.

#### OBW0549

Joined Mar 2, 2015
3,566
Try Googling "frequency to voltage converter."

#### LesJones

Joined Jan 8, 2017
3,475
Your question contradicts itself. You say NO integrated circuit but then you say you can use opamps. (Which will be integrated circuits unless you build them yourself using discrete components.) Another tip Google "charge pumps"

Les.

#### RBR1317

Joined Nov 13, 2010
662
Your question contradicts itself. You say NO integrated circuit but then you say you can use opamps.
I took that to mean NO F2V IC such as the LM2907. Note that at the heart of the LM2907 is a charge pump.

#### absf

Joined Dec 29, 2010
1,949
Here's one with any IC. But the maths is quite involved....

Allen

#### MrAl

Joined Jun 17, 2014
8,470
Hi,

A quick example which would be the most basic F to V converter is a one shot that outputs a very narrow pulse and that pulse is integrated with a fixed time constant and some leakage. The output voltage is related to the input frequency by a constant, although the linearity may not be as good as you want because of the narrow pulse and the leakage. This is the most basic way to do it but also probably the worst way to do it too.

You should try to figure this out too and see what makes sense to you.