PLL Circuit

CMOS PLL circuit

One of the most interesting projects to work with is that of a synthesizer that can accurately gnerate desired frequencies. This synthesizer uses just three CMOS chips and one PNP transistor. It is a fact that the transistor may be the hardest component to get in some parts of the world!! The synthesizer will generate a 3:1 frequency range anywhere from 300Hz to 4,000,000Hz (4MHz). Using the components shown you can feed the synthesizer with up to 12vDC but with only 9vDC the synthesizer may not achieve more than 3.5MHz. Tye lock-range of this synthesizer is about 10:1 or so...

FM Transmitter with PLL

In order to simplify the transmitter design, we've used the new pll circuit from Motorola :the MC145170. This PLL includes the prescaler and a serial standard bus called SPI. We advise to use the P2 version that fixes some init issues during the Power Up. This PLL circuit is definitely smaller than the old one, consequently we've added on the radio board, the power control circuit that allows to switch on, the RF signal when the lock detect is established. In fact a simple LM317 that supplies the last RF stage, is controled by the lock detect signal through the ADJ pin. The oscillator and the RF driver stages have been improved to get a better harmonics rejection than the previous version. We have replaced the BB204 varactors by new ones: BB209...

FM PLL transmitter

This new FM transmitter is very easy to make and doesn't need any RF tuning. First of all ,we have used an integrated VCO: The POS150 from Mini-circuits. This excellent RF circuit covers all the FM Band in a voltage range of 4V to 8V. The Kvco factor is very stable all over the FM band, consequently, we have applied the AF signal directly on the control voltage line coming from the PLL. A 4dB attenuator allows the VCO to drive the MSA1105 RF power stage without exceeding the 1dB gain compression. Finally,a low pass filter ensures a good harmonics rejection.(H3<-60dBc). This new design conducts to new RF performances like: Phase/noise equals to -103dBc/Hz at 10KHz from the carrier.. +17dBm output power level (50mW)...

PLL 41MHz reciever with 68HC711D3

The quartz QZ1 of the preceding receivers which set the work frequency is not on the market any more. It is replaced by a locking phase loop allowing the free choice of an unspecified frequency on the band used, either the 41, or the 72 MHz. The step between channels is 5 kHz, giving us 101 frequencies in 72 MHz and 41 in 41 MHz. In practice, the RX19 " scans " on the 2 frequencies chosen by the user. The first is called a Normal Frequency (Fn) and he other, a Safety Frequency (Fs). In fact, one does not take precedence over the other, except that when turning the power on, the RX19 starts by using Fn. In addition, it will use whichever signal of either Fn or Fs it will receive clearly...

FM PLL transmitter 88-108MHz with PIC16F870

This transmitter is PLL controlled and the frequency is very stable and can be programmed digitally. The transmitter will work from 88 to 108 MHz and the output power is up to 500mW. With minor changes the frequency can be set from 50 to 150 MHz. The main oscillator is based around the transistor T1. This oscillator is called Colpitts oscillator and it is voltage controlled to achieve FM (frequency modulation) and PLL control. T1 should be a HF transistor to work well, but in this case I have used a cheap and common BC817 transistor. The oscillator needs a LC tank to oscillate properly. In this case the LC tank consist of L1 with C1, C2, C3, and the varicap BB139. The coil is parallel with C1 and C2 which are in serial . The same with the varicap and C3. You can think that L is parallel with [ (C1//C2) + (Varicap//C3)] ..

FM PLL controlled VCO

The main oscillator is printed in blue and is voltage controlled. In this construction the VCO range is 88 to 108 MHz. As you can see from the blue arrows, some energy goes to an amplifier and some energy goes to the PLL unit. You can also see that the PLL can control the frequency of the VCO. What the PLL do is that it compare the VCO frequency with the reference frequency (which is very stable) and then regulated the VCO voltage to lock the oscillator at desired frequency. The last part that will affect the VCO is the audio input. The amplitude of the audio will make the VCO change in frequnency FM (Frequency Modulation). I will explain it all in detail under section Hardware and schematic. ..

TV-tuner receiver

The MC13136 circuit is not easy to find so I have replaced it with a new receiver circuit called SA615. This is a basic FM receiver with very good performance and sensitivity. In my super receiver I used a DDS to fine tune the receiver, but in this project I replaced it with a PLL synthesizer. I have decided the oscillator frequency of the FM receiver to be 38.9MHz. See figure at right. This FM receiver has an IF frequency of 455kHz and that means it will receive RF signal at 38.9MHz ±455kHz. That means two places. One reception will be at 38.445MHz and the other will be at 39.335MHz...

5W PLL FM Transmitter (PIC16F627A)

The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD display. Some experience with building devices of this kind are highly recommended. After complete parts placement: Check that there are no shorts bridging adjacent tracks or pads. Check electrolytic capacitors polarity and semiconductor parts orientation. Make any duty load and connect it temporarily to the antenna connector. Use for example 2 or 3 bulbs (24V/170mA or 24V/3W) in parallel...

5W Chinese PLL FM Transmitter With LCD Printed Circuit Board (PCB)

Here's PLL FM transmitter circuit from china. This circuit uses the familiar 2SC1971 for final power amplifier stage. The PLL controller of the FM transmitter use SAA1057 and PIC16F628 (download HEX file)...

Stereo PLL FM transmitter

This is the latest BH1417 FM Transmitter design from RHOM that includes a lot of features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, stereo encoder for stereo transmission, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference, PLL circuit that provides rock solid frequency transmission (no more frequency drift), FM oscillator and RF output buffer. There are 14 possible transmission frequencies with 200KHz increments that users can select with a 4-DIP switch. Lower band frequencies start from 88.7 up to 89.9 MHz, and upper band frequencies start from 107.7 up to 108.9 MHz. ..

The circuit is a divider by 64 used in many RF applications like as satellite receiver, digital tuners, frequency counters, PLL, etc. The heart of circuit is an IC named SAB6456, but you can use SDA2101 or other equivalent chips. Each output is NOT of the other...

Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW VHF amplifier so it should be fairly easy for anyone to build. It also includes built-in pre-emphasis and C5 for enhanced sound quality. While assembling the transmitter care must be taken to make sure that C1 is directly connected to L1 and C9 to L2. These caps eliminate the distortions form the DC supply and improve the sound quality greatly. 9V voltage supply is also very important because it provides the exact amount of current to Q1 to produce loud and clear sound quality...

This PLL can operate over a wide frequency range, not just 1 or 2 octaves but over 1 or 2 or 3 decades. It naturally provides a voltage output which responds quickly to frequency changes, yet does not have any inherent ripple. Thus, it can be used as a frequency-to-voltage (F-to-V) converter..

The circuit in Figure 1 stems from a radio-controlled modeling application, which requires a voltage proportional to the width of the incoming servo pulses. The circuit is optimized for a positive-going pulse width of 1 to 2 msec, repeating at intervals of approximately 17 msec. The output produces a voltage of 0.95V for a 1-msec pulse to 2.25V for a 2-msec pulse. The circuit operates similarly to a PLL, but it locks onto the pulse width, rather than to the frequency, of the incoming signal...

The TDA1591 is a monolithic bipolar integrated circuit providing the stereo decoder function and noise blanking for FM car radio applications...