Analog Frequency Dividers

before you start building PPL circuit (i know, i know, just messing with Nigel ) you really should tell what are you trying to do.

you told us you have function generator and you need additional circuitry to change signal frequency. why? can't you simply adjust the desired frequency on the generator itself? that's what they are for...
it is much simpler to generate sine of specific frequency that to sinthesize it from another - specially if the accuracy is important.

assume you got the circuit. what are you going to do with the signal?
test audio amplifiers, tune guitar or piano or whatever...?

To Test Keyboard organs,synths,test audio amplifiers

How do i put a Sine wave 1Khz input in a PLL circuit with a output thats half the frequency?

How do i put a Sine wave 1Khz input in a CML circuit with a output thats half the frequency?

I'm new to this PLL and CML circuit never worked or built them how do i start this are PLL and CML in a Digital circuit book because i can't find any PLL or CML circuit in any of my analog or digiatl books where do i start please?

How does the PLL circuit Divide the frequency Digitally or analog ?
Whats kind of PLL circuit does this?

How does the CML circuit Divide the frequency Digitally or analog ?
Whats kind of CML circuit does this?

walters said:

To Test Keyboard organs,synths,test audio amplifiers

How do i put a Sine wave 1Khz input in a PLL circuit with a output thats half the frequency?

How do i put a Sine wave 1Khz input in a CML circuit with a output thats half the frequency?

I'm new to this PLL and CML circuit never worked or built them how do i start this are PLL and CML in a Digital circuit book because i can't find any PLL or CML circuit in any of my analog or digiatl books where do i start please?

How does the PLL circuit Divide the frequency Digitally or analog ?
Whats kind of PLL circuit does this?

How does the CML circuit Divide the frequency Digitally or analog ?
Whats kind of CML circuit does this?

Click to expand...

I don't know what a CML is?.

But a PLL (Phase Locked Loop) is a VERY common circuit, your television includes a number of them, as does your mobile phone.

Basically it consists of a number of elements.

1) VCO (Voltage Controlled Oscillator), in your case this needs to be a sinewave VCO, as you want a sinewave output.

2) Reference frequency, in your case this will be the incoming frequency.

3) Phase comparator, this compares the frequency and phase of the two frequencies, and outputs an error voltage - this control voltage feeds the VCO, and adjusts it's frequency until the two match.

So the two oscillators are 'phase locked' to each other.

If you now add a digital divide by two circuit between the VCO and the phase comparator, the VCO will now run at TWICE the reference frequency, as the output of the divide by 2 is locked to the reference.

Likewise if you place the divide by two between the reference and phase comparator, then the VCO will run at HALF the reference frequency.

By careful planning of the division ratios, and using switched dividers, you can get any frequency you want.

Obviously the VCO has to cover the required range though!.

Notice that all the dividing is digital, and the phase comparator is comparing digital signals, but the VCO itself is a sinewave.

If you do a goole for "phase locked loop" you will find plenty of information.

Organ Tuning Aid

A-ha ! musical notes

Rather than a PLL circuit I would suggest a microcontroller.
Run it from a 10MHz crystal oscillator and let the microcontroller do counting to produce semitones. This could be done with any old PIC and the results are as accurate as the ancient (and very obsolite) top octave generator IC that allmost all electronic organs used to be based on.
All the outputs would be square wave but that isn't a huge problem.

If you want better accuracy then you need a higher frequency to divide by or consider a DDS circuit (direct digital synthesis - an AD9850 would eat this job !) and the output would be a very clean sine wave :wink:

The old organ used a the frequency of a oscillator and used Flip flops to
divide the frequency down or up

How did they use Flip flops to divide up or down the frequency?

The flip flops in my digital books are just for switching not used for
dividing the frequency what type of flip flop circuits is this?

the first of which which used twelve oscillators to produce one octave of chromatic scale, and frequency dividers to produce other notes.

Most electronic organs use "divide down" circuitry to produce the various pitches needed for the organ. Each tone generator has two sections....a master oscillator and the dividers. The job of the master oscillator (M.O.) is to produce the highest tone of that note, say the highest A note that the organ might need. Then the output of the M.O. is routed through a divider that halves the frequency of the M.O., producing an octave lower pitch for the next lower A. This process is repeated as many times as there are octaves in the keybed, and you then have the pitch basis for the organ. Tonal colors are varied in this type of organ by switching in various capacitors that make the tone bright or dark.

the oscillator was then passed through a series of 5 frequency dividers to create a further two octaves.

Each divider takes the output from the previous stage, and divides it in half, producing the next lower octave.

You only have to tune each of the twelve oscillators - the dividers are not tunable.

standard 12 oscillators/divider setup

Each frequency divider is a non-linear amplifier operating in such a manner that its output signal has half the frequency of its input signal, and therefore the musical interval between two consecutive dividers is one octave. Referring to Figure 12, it may be seen how the dividers are cascaded and thereby supply the different octaves of the note "A".


the outputs of high-frequency oscillators are 'divided down' by integer factors to create the correct pitches for all the notes of the top octave of the keyboard, and these are then further divided by factors of two to generate each octave beneath. However, organ designers discovered that they could divide the master oscillators in different ways to generate two frequencies for each note that were almost, but not exactly the same.

walters said:

The old organ used a the frequency of a oscillator and used Flip flops to
divide the frequency down or up

How did they use Flip flops to divide up or down the frequency?

The flip flops in my digital books are just for switching not used for
dividing the frequency what type of flip flop circuits is this?

Click to expand...

A flip flop (bistable multivibrator) divides by two, and was commonly used in old electronic organs. As we've repeatedly said, you CAN'T divide down, so (as you next post says) you generate the highest octave with 12 oscillators, and divide down repeatedly from those to get the other octaves. As also explained previously, the output of the bistables will be square waves, and these then needed filtering to produce the tone required.

If this is the sort of thing you're asking about?, it bears no resemblance to anything you've previously asked!.

A flip flop (bistable multivibrator) divides by two, and was commonly used in old electronic organs.

Yes i want to use Sine Wave inputs that divide the Sine wave frequency
what circuit would do this?
To divide the Frequency of Sine Waves?

Are Oscillators Frequencys Sine waves?

How do divide the oscillators sine wave frequencys?

Block diagram:

Sine wave>>>Flip flop>>>divides the freq down>>>Square wave output


A flip flop (bistable multivibrator) divides by two
Most of the Flip flops in my digital book are just switching flip flops i don't
see any Frequency based flip flops

So i put a sine wave in the input of a flip flop and the output of the flip flop with be a Square wave but half of the freqency of the inputs freqency
HOW do i set the Flip flops resistors or capacitors to a FIX Frequency to?

What sets the Flip Flops Freqency?
What sets the Flip Flop to Divided?